Study of Philosophy

Philosophy is the study of general and fundamental problems, such as those connected with existence, knowledge, values, reason, mind, and language. Philosophy is distinguished from other ways of addressing such problems by its critical, generally systematic approach and its reliance on rational argument. The word "philosophy" comes from the Greek φιλοσοφία (philosophia), which literally means "love of wisdom".

Branches of philosophy

The following branches are the main areas of study:

  • Metaphysics is the study of the nature of reality, including the relationship between mind and body, substance and accident, events and causation. Traditional branches are cosmology and ontology.
  • Epistemology is concerned with the nature and scope of knowledge, and whether knowledge is possible. Among its central concerns has been the challenge posed by skepticism and the relationships between truth, belief, and justification.
  • Ethics, or "moral philosophy", is concerned primarily with the question of the best way to live, and secondarily, concerning the question of whether this question can be answered. The main branches of ethics are meta-ethics, normative ethics, and applied ethics. Meta-ethics concerns the nature of ethical thought, such as the origins of the words good and bad, and origins of other comparative words of various ethical systems, whether there are absolute ethical truths, and how such truths could be known. Normative ethics are more concerned with the questions of how one ought to act, and what the right course of action is. This is where most ethical theories are generated. Lastly, applied ethics go beyond theory and step into real world ethical practice, such as questions of whether or not abortion is correct.  Ethics is also associated with the idea of morality, and the two are often interchangeable.
  • Logic is the study of valid argument forms. Beginning in the late 19th century, mathematicians such as Gottlob Frege focused on a mathematical treatment of logic, and today the subject of logic has two broad divisions: mathematical logic (formal symbolic logic) and what is now called philosophical logic.

Philosophy has expanded to include specialized branches of thought:

  • Philosophy of language explores the nature, the origins, and the use of language.
  • Philosophy of law (more commonly called jurisprudence) explores the varying theories explaining the nature and the interpretations of the law in society.
  • Philosophy of mind explores the nature of the mind, and its relationship to the body, and is typified by disputes between dualism and materialism. In recent years there has been increasing similarity between this branch of philosophy and cognitive science.
  • Philosophy of religion
  • Philosophy of science
  • Political philosophy is the study of government and the relationship of individuals (or families and clans) to communities including the state. It includes questions about justice, law, property, and the rights and obligations of the citizen. Politics and ethics are traditionally inter-linked subjects, as both discuss the question of what is good and how people should live.
  • Aesthetics deals with beauty, art, enjoyment, sensory-emotional values, perception, and matters of taste and sentiment.

Many academic disciplines also have philosophical foundations. These include history, logic, law, and mathematics. In addition, a range of disciplines have emerged to address areas that historically were the subjects of philosophy. These include anthropology, psychology, and physics.


By Kurt von Fritz, Albert William Levi, The Rev. Armand Maurer, C.S.B., Avrum Stroll, Richard Wolin

The Western Tradition
It would be difficult if not impossible to find two philosophers who would define philosophy in exactly the same way. Throughout its long and varied history in the West, philosophy has meant many different things. Some of these have been a search for wisdom (the meaning closest to the Latin philosophia, itself derived from the Greek philosoph, “lover of wisdom”); an attempt to understand the universe as a whole; an examination of humankind’s moral responsibilities and social obligations; an effort to fathom the divine intentions and the place of human beings with reference to them; an effort to ground the enterprise of natural science; a rigorous examination of the origin, extent, and validity of human ideas; an exploration of the place of will or consciousness in the universe; an examination of the values of truth, goodness, and beauty; and an effort to codify the rules of human thought in order to promote rationality and the extension of clear thinking. Even these do not exhaust the meanings that have been attached to the philosophical enterprise, but they give some idea of its extreme complexity and many-sidedness.
It is difficult to determine whether any common element can be found within this diversity and whether any core meaning can serve as a universal and all-inclusive definition. But a first attempt in this direction might be to define philosophy either as “a reflection upon the varieties of human experience” or as “the rational, methodical, and systematic consideration of those topics that are of greatest concern to humankind.” Vague and indefinite as such definitions are, they do suggest two important facts about philosophizing: (1) that it is a reflective, or meditative, activity and (2) that it has no explicitly designated subject matter of its own but is a method or type of mental operation (like science or history) that can take any area or subject matter or type of experience as its object. Thus, although there are a few single-term divisions of philosophy of long standing—such as logic, ethics, epistemology, or metaphysics—its divisions are probably best expressed by phrases that contain the preposition of—such as philosophy of mind, philosophy of science, philosophy of law, and philosophy of art (aesthetics).
Part of what makes it difficult to find a consensus among philosophers about the definition of their discipline is precisely that they have frequently come to it from different fields, with different interests and concerns, and that they therefore have different areas of experience upon which they find it especially necessary or meaningful to reflect. St. Thomas Aquinas (c. 1224–75), a Dominican friar, George Berkeley (1685–1753), a bishop of the Irish Church, and Søren Kierkegaard (1813–55), a Danish divinity student, all saw philosophy as a means to assert the truths of religion and to dispel the materialistic or rationalistic errors that, in their opinion, had led to its decline. Pythagoras (c. 580–c. 500 bc) in southern Italy, René Descartes (1596–1650) in France, and Bertrand Russell (1872–1970) in England were primarily mathematicians whose views of the universe and of human knowledge were vastly influenced by the concept of number and by the method of deductive thinking. Some philosophers, such as Plato (c. 428–c. 348 bc), Thomas Hobbes (1588–1679) and John Stuart Mill (1806–73), were obsessed by problems of political arrangement and social living, so that whatever they have done in philosophy has been stimulated by a desire to understand and, ultimately, to change the social and political behaviour of human beings. And still others—such as the Milesians (the first philosophers of Greece, from the ancient Anatolian city of Miletus), Francis Bacon (1561–1626), an Elizabethan philosopher, and Alfred North Whitehead (1861–1947), an English metaphysician—began with an interest in the physical composition of the natural world, so that their philosophies resemble more closely the generalizations of physical science than those of religion or sociology.
The history of Western philosophy reveals in detail the concentrated activity of a multitude of serious and able thinkers reflecting upon, reasoning about, and considering deeply the nature of their experience. But throughout this diversity certain characteristic oppositions continually recur, such as those between monism, dualism, and pluralism in metaphysics (see pluralism and monism); between materialism and idealism in cosmological theory; between nominalism and realism in the theory of signification; between rationalism and empiricism in epistemology; between utilitarianism and deontological ethics in moral theory; and between partisans of logic and partisans of emotion in the search for a responsible guide to the wisdom of life.
Many of these fundamental oppositions among philosophers will be treated in the article that follows. But if any single opposition is taken as central throughout the history of Western philosophy at every level and in every field, it is probably that between the critical and the speculative impulses. These two divergent motivations tend to express themselves in two divergent methods: analysis and synthesis, respectively. Plato’s Republic is an example of the second; the Principia Ethica (1903) of G.E. Moore (1873–1958), a founder of analytic philosophy, is an example of the first. Beginning with a simple question about justice, the Republic in its discursiveness slowly but progressively brings more and more areas into the discussion: first ethics, then politics, then educational theory, then epistemology, and finally metaphysics. Starting with one specific question, Plato finally managed to make his discussion as broad as the world. Principia Ethica does just the opposite. Beginning with a general question—What is good?—it progressively breaks up this question into a whole series of subordinate questions, analyzing meanings ever more minutely, growing narrower and narrower but always with the utmost modesty and sincerity, striving for increasing simplicity and exactitude.
The analytic, or critical, impulse treats any subject matter or topic by concentrating upon the part, by taking it apart in the service of clarity and precision. It was essentially the method of Aristotle (384–322 bc) and of Peter Abelard (1079–1142), a French Scholastic; of David Hume (1711–76), a Scottish skeptic, and of Rudolf Carnap (1891–1970), a German American logical positivist; and of Russell and Moore. The synthetic, or speculative, impulse operates by seeking to comprehend the whole, by putting it all together in the service of unity and completeness. It is essentially the method of Parmenides, a Sophist, and of Plato; of Aquinas and of Benedict de Spinoza (1632–77), a Dutch Jewish rationalist; and of Georg Wilhelm Friedrich Hegel (1770–1831), a German idealist, and of Whitehead. Throughout philosophy’s history, each of the two traditions has made its insistent claim.
There is one philosophical tradition—that of logical positivism—that sees philosophy as originating in the obscure mists of religion and coming finally to rest in the pure sunshine of scientific clarity. This represents a necessary progress because logical positivism considers it a scandal when philosophers speak in statements that are not in principle “verifiable” (see verifiability principle); it holds that bold and adventuresome philosophical speculation is at best mere self-indulgence, a passing state occurring when philosophical problems are raised prematurely—that is, at a time when philosophy does not possess the means to solve them.
Although logical positivism represents a partisan view, it does express indirectly a basic truth—that the philosophical enterprise has always hovered uncertainly between the lure of religious devotion and that of scientific exactitude. In the teachings of the earliest philosophers of Greece, it is impossible to separate ideas of divinity and the human soul from ideas about the mystery of being and the genesis of material change, and in the Middle Ages philosophy was acknowledged to be the “handmaiden of theology.” But the increased secularization of modern culture has largely reversed this trend, and the Enlightenment’s emphasis upon the separation of nature from its divine creator has increasingly placed philosophical resources at the disposal of those interested in creating a philosophy of science.
Yet philosophy’s continuing search for philosophical truth leads it to hope, but at the same time to profoundly doubt, that its problems are objectively solvable. With respect to a total description of Being or a definitive account of the nature of values, only individual solutions now seem possible; and the optimistic hope for objective answers that secure universal agreement must be given up.
In this respect, philosophy seems less like science than like art and philosophers more like artists than like scientists, for their philosophical solutions bear the stamp of their own personalities, and their choice of arguments reveals as much about themselves as their chosen problem. As a work of art is a portion of the world seen through a temperament, so a philosophical system is a vision of the world subjectively assembled. Plato and Descartes, Immanuel Kant (1724–1804), a German idealist, and John Dewey (1859–1952), an American pragmatist, have given to their systems many of the quaint trappings of their own personalities.
But if philosophy is not true in the same sense as science, it is not false in the same sense either; and this gives to the history of philosophy a living significance that the history of science does not enjoy. In science, the present confronts the past as truth confronts error; thus, for science, the past, even when important at all, is important only out of historical interest. In philosophy it is different. Philosophical systems are never definitively proved false; they are simply discarded or put aside for future use. And this means that the history of philosophy consists not simply of dead museum pieces but of ever-living classics—comprising a permanent repository of ideas, doctrines, and arguments and a continuing source of philosophical inspiration and suggestiveness to those who philosophize in any succeeding age. It is for this reason that any attempt to separate philosophizing from the history of philosophy is both a provincial act and an unnecessary impoverishment of its rich natural resources.

General considerations

Ways of Ordering The History
The writing of the history of philosophy is controlled by a variety of cultural habits and conventions.
The ensuing article on the history of Western philosophy is divided into five sections—ancient, medieval, Renaissance, modern, and contemporary. A threefold distinction between ancient, medieval, and modern philosophy was prevalent until recent times and is only as old as the end of the 17th century. This distinction slowly spread to historical writing in all fields and was given definitive influence in philosophical writing through the series of lectures on the history of philosophy that Hegel delivered first at Jena, then at Heidelberg, and finally at Berlin between 1805 and 1830. In the century after Hegel, it was taken for granted as standard practice, though a host of cultural assumptions is implied by its use.
Treatment of the total field of the history of philosophy has been traditionally subject to two types of ordering, according to whether it was conceived primarily as (1) a history of ideas or (2) a history of the intellectual products of human beings. In the first ordering, certain ideas, or concepts, are viewed as archetypal (such as matter or mind or doubt), and the condensations occurring within the flow of thought tend to consist of basic types, or schools. This ordering has characterized works such as The History of Materialism (1866) by Friedrich Lange (1828–75), The Idealist Tradition: From Berkeley to Blanshard (1957) by A.C. Ewing (1899–1973), and The History of Scepticism from Erasmus to Descartes (1960) by Richard H. Popkin (1923–2005). In the second type of ordering, the historian, impressed by the producers of ideas as much as by the ideas themselves—that is, with philosophers as agents—reviews the succession of great philosophical personalities in their rational achievements. This ordering has produced the more customary histories, such as A History of Western Philosophy (1945) by Bertrand Russell and The Great Philosophers (1957) by Karl Jaspers (1883–1969).
These two different types of ordering depend for their validity upon an appeal to two different principles about the nature of ideas, but their incidental use may also be influenced by social or cultural factors. Thus, the biographers and compilers of late antiquity (among them Plutarch [46–c. 119], Sextus Empiricus [flourished 3rd century ad], Philostratus [170–c. 245], and Clement of Alexandria [150–c. 211]), impressed by the religious pluralism of the age in which they lived, thought of philosophers, too, as falling into different sects and wrote histories of the Sophists, the Skeptics, the Epicureans, and other such schools; whereas, almost 2,000 years later, Hegel—living in a period of Romantic historiography dominated by the concept of the great man in history—deliberately described the history of philosophy as “a succession of noble minds, a gallery of heroes of thought.”
Moving between these two ordering principles, the article below will be eclectic (as has come to be the custom), devoting chief attention to outstanding major figures while joining more-minor figures, wherever possible, into the schools or tendencies that they exemplify.
Factors In Writing The History
The type of ordering suggested above also has some relationship to the more general problems of method in the writing of the history of philosophy. Here there are at least three factors that must be taken into account: (1) that any philosopher’s doctrines depend (at least in part) upon those of his predecessors, (2) that a philosopher’s thought occurs at a certain point in history and thus expresses the effects of certain social and cultural circumstances, and (3) that a philosopher’s thought stems (at least in part) from his own personality and situation in life. This is only to say that the history of philosophy, to be at all comprehensive and adequate, must deal with the mutual interplay of ideas, of cultural contexts, and of agents.
The first factor may be called logical because a given philosophy is, in part, the intellectual response to the doctrines of its forerunners, taking as central the problems given by the current climate of controversy. Thus, many of the details of Aristotle’s ethical, political, and metaphysical systems arise in arguments directed against statements and principles of Plato; much of An Essay Concerning Human Understanding (1690) by the English philosopher John Locke (1632–1704), an initiator of the Enlightenment, is directed against contemporary Cartesian presuppositions; and the New Essays Concerning Human Understanding (1704) by Gottfried Wilhelm Leibniz (1646–1716), a broadly learned German rationalist, is, in turn, specifically directed against Locke.
The second factor may be called sociological because it considers philosophy, at least in part, as a direct form of social expression, arising at a certain moment in history, dated and marked by the peculiar problems and crises of the society in which it flourishes. From this perspective, the philosophy of Plato may be viewed as the response of an aristocratic elitism to the immediate threat of democracy and the leveling of values in 5th-century Athens—its social theory and even its metaphysics serving the movement toward an aristocratic restoration in the Greek world. Thus, the philosophy of St. Thomas Aquinas may be viewed as an effort toward doctrinal clarification in support of the institution of the medieval Roman Catholic Church, as the saint spent his life obediently fulfilling the philosophical tasks set for him by his superiors in the church and the Dominican order. Thus, the philosophy of Kant, with all of its technical vocabulary and rigid systematization, may be viewed as an expression of the new professionalism in philosophy, a clear product of the rebirth of the German universities during the 18th-century Enlightenment.
The third factor may be called biographical, or individual, because, with Hegel, it recognizes that philosophies are generally produced by people of unusual or independent personality, whose systems usually bear the mark of their creators. And what is meant here by the individuality of the philosopher lies less in the facts of his biography (such as his wealth or poverty) than in the essential form and style of his philosophizing. The cool intensity of Spinoza’s geometric search for wisdom, the unswerving (if opaque) discursiveness of Hegel’s quest for completeness or totality, the relentless and minute analytic search for distinctions and shades of meaning that marks Moore’s master passion (“to be accurate—to get everything exactly right”)—these qualities mark the philosophical writings of Spinoza, Hegel, and Moore with an unmistakably individual and original character.
Shifts In the Focus and Concern of Western Philosophy
Any adequate treatment of individual figures in the history of philosophy tries to utilize this threefold division of logical, sociological, and individual factors; but in a synoptic view of the history of philosophy in the West, one is particularly aware of the various shifts of focus and concern that philosophy has sustained and, indeed, of the often profound differences in the way that it defines itself or visualizes its task from age to age or from generation to generation.
Philosophy among the Greeks slowly emerged out of religious awe into wonder about the principles and elements of the natural world. But as the Greek populations more and more left the land to become concentrated in their cities, interest shifted from nature to social living; questions of law and convention and civic values became paramount. Cosmological speculation partly gave way to moral and political theorizing, and the preliminary and somewhat fragmentary questionings of Socrates and the Sophists turned into the great positive constructions of Plato and Aristotle. With the political and social fragmentation of the succeeding centuries, however, philosophizing once again shifted from the norm of civic involvement to problems of salvation and survival in a chaotic world.
The dawn of Christianity brought to philosophy new tasks. St. Augustine (354–430)—the philosophical bishop of Hippo—and the Church Fathers used such resources of the Greek tradition as remained (chiefly Platonism) to deal with problems of creation, of faith and reason, and of truth. New translations in the 12th century made much of Aristotle’s philosophy available and prepared the way for the great theological constructions of the 13th century, chiefly those of the Scholastic philosophers St. Bonaventure (c. 1217–74), St. Albertus Magnus (c. 1200–80), St. Thomas Aquinas, Roger Bacon (c. 1220–92), and John Duns Scotus (c. 1266–1308). The end of the Middle Ages saw a new flowering of the opposite tendencies in the nominalism of William of Ockham (c. 1285–c. 1347) and the mysticism of Meister Eckhart (c. 1260–c. 1327).
The Middle Ages gave way to the Renaissance. Universalism was replaced by nationalism. Philosophy became secularized. The great new theme was that of the mystery and immensity of the natural world. 
The best philosophical minds of the 17th century turned to the task of exploring the foundations of physical science, and the symbol of their success—the great system of physics constructed by Sir Isaac Newton (1642–1727)—turned the philosophers of the Enlightenment to epistemology and to the examination of the human mind that had produced so brilliant a scientific creation. The 19th century, a time of great philosophical diversity, discovered the irrational, and in so doing prepared the way for the 20th-century oppositions between logical atomism and phenomenology and between logical positivism and existentialism.
Although the foregoing capsule presentation of the history of philosophy in the West follows a strict chronology, it does not do justice to the constant occurrence and recurrence of dominant strands in the history of thought. It would also be possible to write the philosophical history of the Middle Ages simply by noting the complicated occurrence of Platonic and Aristotelian doctrines, of the Renaissance according to the reappearance of ancient materialism, Stoicism, and skepticism, and of the 18th century in terms of the competing claims of rationalist and empiricist principles. Thus, chronology and the interweaving of philosophical systems cooperate in a history of philosophy.

Ancient Greek and Roman philosophy

The pre-Socratic philosophers
Cosmology and The Metaphysics of Matter
Because the earliest Greek philosophers focused their attention upon the origin and nature of the physical world, they are often called cosmologists, or naturalists. Although monistic views (which trace the origin of the world to a single substance) prevailed at first, they were soon followed by several pluralistic theories (which trace it to several ultimate substances).
Monistic cosmologies
There is a consensus, dating back at least to the 4th century bc and continuing to the present, that the first Greek philosopher was Thales of Miletus (flourished 6th century bc). In Thales’ time the word philosopher (“lover of wisdom”) had not yet been coined. Thales was counted, however, among the legendary Seven Wise Men (Sophoi), whose name derives from a term that then designated inventiveness and practical wisdom rather than speculative insight. Thales demonstrated these qualities by trying to give the mathematical knowledge that he derived from the Babylonians a more exact foundation and by using it for the solution of practical problems—such as the determination of the distance of a ship as seen from the shore or of the height of the Egyptian pyramids. Although he was also credited with predicting an eclipse of the Sun, it is likely that he merely gave a natural explanation of one on the basis of Babylonian astronomical knowledge.
Thales is considered the first Greek philosopher because he was the first to give a purely natural explanation of the origin of the world, free from mythological ingredients. He held that everything had come out of water—an explanation based on the discovery of fossil sea animals far inland. His tendency (and that of his immediate successors) to give nonmythological explanations was undoubtedly prompted by the fact that all of them lived on the coast of Asia Minor, surrounded by a number of nations whose civilizations were much further advanced than that of the Greeks and whose own mythological explanations varied greatly. It appeared necessary, therefore, to make a fresh start on the basis of what a person could observe and infer by looking at the world as it presented itself. This procedure naturally resulted in a tendency to make sweeping generalizations on the basis of rather restricted, though carefully checked, observations.
Thales’ disciple and successor, Anaximander of Miletus (610–c. 546 bc), tried to give a more elaborate account of the origin and development of the ordered world (the cosmos). According to him, it developed out of the apeiron (“unlimited”), something both infinite and indefinite (without distinguishable qualities). Within this apeiron something arose to produce the opposites of hot and cold. These at once began to struggle with each other and produced the cosmos. The cold (and wet) partly dried up (becoming solid earth), partly remained (as water), and—by means of the hot—partly evaporated (becoming air and mist), its evaporating part (by expansion) splitting up the hot into fiery rings, which surround the whole cosmos. Because these rings are enveloped by mist, however, there remain only certain breathing holes that are visible to human beings, appearing to them as the Sun, Moon, and stars. Anaximander was the first to realize that upward and downward are not absolute but that downward means toward the middle of the Earth and upward away from it, so that the Earth had no need to be supported (as Thales had believed) by anything. 
Starting from Thales’ observations, Anaximander tried to reconstruct the development of life in more detail. Life, being closely bound up with moisture, originated in the sea. All land animals, he held, are descendants of sea animals; because the first humans as newborn infants could not have survived without parents, Anaximander believed that they were born within an animal of another kind—specifically, a sea animal in which they were nurtured until they could fend for themselves. Gradually, however, the moisture will be partly evaporated, until in the end all things will return into the undifferentiated apeiron, “in order to pay the penalty for their injustice”—that of having struggled against one another.
Anaximander’s successor, Anaximenes of Miletus (flourished c. 545 bc), taught that air was the origin of all things. His position was for a long time thought to have been a step backward because, like Thales, he placed a special kind of matter at the beginning of the development of the world. But this criticism missed the point. Neither Thales nor Anaximander appear to have specified the way in which the other things arose out of water or apeiron. Anaximenes, however, declared that the other types of matter arose out of air by condensation and rarefaction. In this way, what to Thales had been merely a beginning became a fundamental principle that remained essentially the same through all of its transmutations. Thus, the term arche, which originally simply meant “beginning,” acquired the new meaning of “principle,” a term that henceforth played an enormous role in philosophy down to the present. This concept of a principle that remains the same through many transmutations is, furthermore, the presupposition of the idea that nothing can come out of nothing and that all of the comings to be and passings away that human beings observe are nothing but transmutations of something that essentially remains the same eternally. In this way it also lies at the bottom of all of the conservation laws—the laws of the conservation of matter, force, and energy—that have been basic in the development of physics. Although Anaximenes of course did not realize all of the implications of his idea, its importance can hardly be exaggerated.
The first three Greek philosophers have often been called “hylozoists” because they seemed to believe in a kind of living matter (see hylozoism). But this is hardly an adequate characterization. It is, rather, characteristic of them that they did not clearly distinguish between kinds of matter, forces, and qualities, nor between physical and emotional qualities. The same entity is sometimes called “fire” and sometimes “the hot.” Heat appears sometimes as a force and sometimes as a quality, and again there is no clear distinction between warm and cold as physical qualities and the warmth of love and the cold of hate. To realize these ambiguities is important to an understanding of certain later developments in Greek philosophy.
Xenophanes of Colophon (c. 560–c. 478 bc), a rhapsodist and philosophical thinker who emigrated from Asia Minor to Elea in southern Italy, was the first to articulate more clearly what was implied in Anaximenes’ philosophy. He criticized the popular notions of the gods, saying that people made the gods in their own image. But, more importantly, he argued that there could be only one God, the ruler of the universe, who must be eternal. For, being the strongest of all beings, he could not have come out of something less strong, nor could he be overcome or superseded by something else, because nothing could arise that is stronger than the strongest. The argument clearly rested on the axioms that nothing can come out of nothing and that nothing that exists can vanish.
These axioms were made more explicit and carried to their logical (and extreme) conclusions by Parmenides of Elea (born c. 515 bc), the founder of the so-called school of Eleaticism, of whom Xenophanes has been regarded as the teacher and forerunner. In a philosophical poem, Parmenides insisted that “what is” cannot have come into being and cannot pass away because it would have to have come out of nothing or to become nothing, whereas nothing by its very nature does not exist. There can be no motion either, for it would have to be a motion into something that is—which is not possible since it would be blocked—or a motion into something that is not—which is equally impossible since what is not does not exist. Hence, everything is solid, immobile being. The familiar world, in which things move around, come into being, and pass away, is a world of mere belief (doxa). In a second part of the poem, however, Parmenides tried to give an analytical account of this world of belief, showing that it rested on constant distinctions between what is believed to be positive—i.e., to have real being, such as light and warmth—and what is believed to be negative—i.e., the absence of positive being, such as darkness and cold.
It is significant that Heracleitus of Ephesus (c. 540–c. 480 bc), whose philosophy was later considered to be the very opposite of Parmenides’ philosophy of immobile being, came, in some fragments of his work, near to what Parmenides tried to show: the positive and the negative, he said, are merely different views of the same thing; death and life, day and night, and light and darkness are really one.
Pluralistic cosmologies
Parmenides had an enormous influence on the further development of philosophy. Most of the philosophers of the following two generations tried to find a way to reconcile his thesis that nothing comes into being nor passes away with the evidence presented to the senses. Empedocles of Acragas (c. 490–430 bc) declared that there are four material elements (he called them the roots of everything) and two forces, love and hate, that did not come into being and would never pass away, increase, or diminish. But the elements are constantly mixed with one another by love and again separated by hate. Thus, through mixture and decomposition, composite things come into being and pass away. Because Empedocles conceived of love and hate as blind forces, he had to explain how, through random motion, living beings could emerge. This he did by means of a somewhat crude anticipation of the theory of the survival of the fittest. In the process of mixture and decomposition, the limbs and parts of various animals would be formed by chance. But they could not survive on their own; they would survive only when, by chance, they had come together in such a way that they were able to support and reproduce themselves. It was in this way that the various species were produced and continued to exist.
Anaxagoras of Clazomenae (c. 500–c. 428 bc), a pluralist, believed that because nothing can really come into being, everything must be contained in everything, but in the form of infinitely small parts. In the beginning, all of these particles had existed in an even mixture, in which nothing could be distinguished, much like the indefinite apeiron of Anaximander. But then nous, or intelligence, began at one point to set these particles into a whirling motion, foreseeing that in this way they would become separated from one another and then recombine in the most various ways so as to produce gradually the world in which human beings live. In contrast to the forces assumed by Empedocles, the nous of Anaxagoras is not blind but foresees and intends the production of the cosmos, including living and intelligent beings; however, it does not interfere with the process after having started the whirling motion. This is a strange combination of a mechanical and a nonmechanical explanation of the world.
By far of greatest importance for the later development of philosophy and physical science was an attempt by the atomists Leucippus (flourished 5th century bc) and Democritus (c. 460–c. 370 bc) to solve the Parmenidean problem. Leucippus found the solution in the assumption that, contrary to Parmenides’ argument, the nothing does in a way exist—as empty space. There are, then, two fundamental principles of the physical world, empty space and filled space—the latter consisting of atoms that, in contrast to those of modern physics, are real atoms; that is, they are absolutely indivisible because nothing can penetrate to split them. On these foundations, laid by Leucippus, Democritus appears to have built a whole system, aiming at a complete explanation of the varied phenomena of the visible world by means of an analysis of its atomic structure. This system begins with elementary physical problems, such as why a hard body can be lighter than a softer one. The explanation is that the heavier body contains more atoms, which are equally distributed and of round shape; the lighter body, however, has fewer atoms, most of which have hooks by which they form rigid gratings. The system ends with educational and ethical questions. A sound and cheerful person, useful to his fellows, is literally well composed. Although destructive passions involve violent, long-distance atomic motions, education can help to contain them, creating a better composure. Democritus also developed a theory of the evolution of culture, which influenced later thinkers. Civilization, he thought, is produced by the needs of life, which compel human beings to work and to make inventions. When life becomes too easy because all needs are met, there is a danger that civilization will decay as people become unruly and negligent.
Epistemology of Appearance
All of the post-Parmenidean philosophers, like Parmenides himself, presupposed that the real world is different from the one that human beings perceive. Thus arose the problems of epistemology, or theory of knowledge. According to Anaxagoras, everything is contained in everything. But this is not what people perceive. He solved this problem by postulating that, if there is a much greater amount of one kind of particle in a thing than of all other kinds, the latter are not perceived at all. The observation was then made that sometimes different persons or kinds of animals have different perceptions of the same things. He explained this phenomenon by assuming that like is perceived by like. If, therefore, in the sense organ of one person there is less of one kind of stuff than of another, that person will perceive the former less keenly than the latter. This reasoning was also used to explain why some animals see better at night and others during the day. According to Democritus, atoms have no sensible qualities, such as taste, smell, or colour, at all. Thus, he tried to reduce all of them to tactile qualities (explaining a bright white colour, for instance, as sharp atoms hitting the eye like needles), and he made a most elaborate attempt to reconstruct the atomic structure of things on the basis of their apparent sensible qualities.
Also of very great importance in the history of epistemology was Zeno of Elea (c. 495–c. 430 bc), a younger friend of Parmenides. Parmenides had, of course, been severely criticized because of the strange consequences of his doctrine: that in reality there is no motion and no plurality because there is just one solid being. To support him, however, Zeno tried to show that the assumption that there is motion and plurality leads to consequences that are no less strange. This he did by means of his famous paradoxes, saying that the flying arrow rests since it can neither move in the place in which it is nor in a place in which it is not, and that Achilles cannot outrun a turtle because, when he has reached its starting point, the turtle will have moved to a further point, and so on ad infinitum—that, in fact, he cannot even start running, for, before traversing the stretch to the starting point of the turtle, he will have to traverse half of it, and again half of that, and so on ad infinitum. All of these paradoxes are derived from the problem of the continuum. Although they have often been dismissed as logical nonsense, many attempts have also been made to dispose of them by means of mathematical theorems, such as the theory of convergent series or the theory of sets. In the end, however, the logical difficulties raised in Zeno’s arguments have always come back with a vengeance, for the human mind is so constructed that it can look at a continuum in two ways that are not quite reconcilable.
Metaphysics of Number
All of the philosophies mentioned so far are in various ways historically akin to one another. Toward the end of the 6th century bc, however, there arose, quite independently, another kind of philosophy, which only later entered into interrelation with the developments just mentioned: the philosophy of Pythagoras of Samos (c. 580–c. 500 bc; see also Pythagoreanism). Pythagoras traveled extensively in the Middle East and in Egypt and, after his return to Samos, emigrated to southern Italy because of his dislike of the tyranny of Polycrates (c. 535–522 bc). At Croton and Metapontum he founded a philosophical society with strict rules and soon gained considerable political influence. He appears to have brought his doctrine of the transmigration of souls from the Middle East. Much more important for the history of philosophy and science, however, was his doctrine that “all things are numbers,” which means that the essence and structure of all things can be determined by finding the numerical relations they express. Originally, this, too, was a very broad generalization made on the basis of comparatively few observations: for instance, that the same harmonies can be produced with different instruments—strings, pipes, disks, etc.—by means of the same numerical ratios—1:2, 2:3, 3:4—in one-dimensional extensions; the observation that certain regularities exist in the movements of the celestial bodies; and the discovery that the form of a triangle is determined by the ratio of the lengths of its sides. But because the followers of Pythagoras tried to apply their principle everywhere with the greatest of accuracy, one of them—Hippasus of Metapontum (flourished 5th century bc)—made one of the most fundamental discoveries in the entire history of science: that the side and diagonal of simple figures such as the square and the regular pentagon are incommensurable (i.e., their quantitative relation cannot be expressed as a ratio of integers). At first sight this discovery seemed to destroy the very basis of the Pythagorean philosophy, and the school thus split into two sects, one of which engaged in rather abstruse numerical speculations, while the other succeeded in overcoming the difficulty by ingenious mathematical inventions. Pythagorean philosophy also exerted a great influence on the later development of Plato’s thought.
The speculations described so far constitute, in many ways, the most important part of the history of Greek philosophy because all of the most fundamental problems of Western philosophy turned up here for the first time. One also finds here the formation of a great many concepts that have continued to dominate Western philosophy and science to the present day.
Anthropology and Relativism
In the middle of the 5th century bc, Greek thinking took a somewhat different turn through the advent of the Sophists. The name is derived from the verb sophizesthai, “making a profession of being inventive and clever,” and aptly described the Sophists, who, in contrast to the philosophers mentioned so far, charged fees for their instruction. Philosophically they were, in a way, the leaders of a rebellion against the preceding development, which increasingly had resulted in the belief that the real world is quite different from the phenomenal world. “What is the sense of such speculations?” they asked, since no one lives in these so-called real worlds. This is the meaning of the pronouncement of Protagoras of Abdera (c. 485–c. 410 bc) that “man is the measure of all things, of those which are that they are and of those which are not that they are not.” For human beings the world is what it appears to them to be, not something else; Protagoras illustrated his point by saying that it makes no sense to tell a person that it is really warm when he is shivering with cold because for him it is cold—for him, the cold exists, is there.
His younger contemporary Gorgias of Leontini (flourished 5th century bc), famous for his treatise on the art of oratory, made fun of the philosophers in his book Peri tou mē ontos ē peri physeōs (“On That Which Is Not; or, On Nature”), in which—referring to the “truly existing world,” also called “the nature of things”—he tried to prove (1) that nothing exists, (2) that if something existed, one could have no knowledge of it, and (3) that if nevertheless somebody knew something existed, he could not communicate his knowledge to others.
The Sophists were not only skeptical of what had by then become a philosophical tradition but also of other traditions. On the basis of the observation that different nations have different rules of conduct even in regard to things considered most sacred—such as the relations between the sexes, marriage, and burial—they concluded that most rules of conduct are conventions. What is really important is to be successful in life and to gain influence over others. This they promised to teach. 
Gorgias was proud of the fact that, having no knowledge of medicine, he was more successful in persuading a patient to undergo a necessary operation than his brother, a physician, who knew when an operation was necessary. The older Sophists, however, were far from openly preaching immoralism. They, nevertheless, gradually came under suspicion because of their sly ways of arguing. One of the later Sophists, Thrasymachus of Chalcedon (flourished 5th century bc), was bold enough to declare openly that “right is what is beneficial for the stronger or better one”—that is, for the one able to win the power to bend others to his will.

The seminal thinkers of Greek philosophy

Socrates (c. 470–399 bc) was also widely considered to be a Sophist, though he did not teach for money and his aims were entirely different from theirs. Although there is a late tradition according to which Pythagoras invented the word philosopher, it was certainly through Socrates—who insisted that he possessed no wisdom but was striving for it—that the term came into general use and was later applied to all earlier serious thinkers. In fact, all of the records of Socrates’ life and activity left by his numerous adherents and disciples indicate that he never tried to teach anything directly. But he constantly engaged in conversations with everybody—old and young, high and low—trying to bring into the open by his questions the inconsistencies in their opinions and actions. His whole way of life rested on two unshakable premises: (1) the principle never to do wrong nor to participate, even indirectly, in any wrongdoing and (2) the conviction that nobody who really knows what is good and right could act against it. He demonstrated his adherence to the first principle on various occasions and under different regimes. When, after the Battle of Arginusae (406 bc), the majority of the Athenian popular assembly demanded death without trial for the admirals, Socrates, who on that day happened to be president of the assembly (an office changing daily), refused to put the proposal to a vote because he believed it was wrong to condemn anyone without a fair trial. He refused even though the people threatened him, shouting that it would be terrible if the sovereign people could not do as they pleased.
When, after the overthrow of democracy in Athens in 404 bc, the so-called Thirty Tyrants, who tried to involve everybody in their wrongdoing, ordered him to arrest an innocent citizen whose money they coveted, he simply disobeyed. This he did despite the fact that such disobedience was even more dangerous than disobeying the sovereign people had been at the time of unrestricted democracy. Likewise, in the time of the democracy, he pointed out by his questions the inconsistency of allowing oneself to be swayed by the oratory of a good speaker instead of first inquiring into his capability as a statesman, whereas in private life a sensible citizen would not listen to the oratory of a quack but would try to find the best doctor. When, after the overthrow of democracy, the Thirty Tyrants had many people arbitrarily executed, Socrates asked everybody whether a man was a good shepherd who diminished the number of sheep instead of increasing it; and he did not cease his questioning when Critias, the leader of the Thirty Tyrants, warned him to take heed not to diminish the number of sheep by his own—Socrates’—person. But the most fundamental inconsistency that he tried to demonstrate everywhere was that most people by their actions show that what they consider good, wonderful, and beautiful in others—such as, for instance, doing right at great danger to oneself—they do not consider good for themselves, and what they consider good for themselves they despise and condemn in others. Although these stands won him the fervent admiration of many, especially among the youth, they also caused great resentment among leading politicians, whose inconsistencies and failings were exposed. Although Socrates had survived unharmed through the regime of the Thirty Tyrants—partly because it did not last long and partly because he was supported by some close relatives of their leader, Critias—it was under the restored democracy that he was accused of impiety and of corrupting the youth and finally condemned to death, largely also in consequence of his intransigent attitude during the trial.
After Socrates’ death his influence became a dominating one through the greater part of the history of Greek and Roman philosophy down to the end of antiquity, and it has been significant ever since. Many of his adherents—Plato first among them, but also including the historian Xenophon (431–c. 350 bc)—tried to preserve his philosophical method by writing Socratic dialogues. Some founded schools or sects that perpetuated themselves over long periods of time: Eucleides of Megara (c. 430–c. 360 bc) emphasized the theoretical aspects of Socrates’ thought (see Megarian school), and Antisthenes (c. 445–c. 365 bc) stressed the independence of the true philosopher from material wants. The latter, through his disciple Diogenes of Sinope (died c. 320 bc), who carried voluntary poverty to the extreme and emphasized freedom from all conventions, became the founder of the sect of the Cynics. Aristippus of Cyrene (c. 435–366 bc), traditional founder of the Cyrenaic school, stressed independence from material goods in a somewhat different way, declaring that there is no reason why a philosopher should not enjoy material goods as long as he is completely indifferent to their loss. Although Aristippus renounced his son because he led a dissolute life, the school that he founded (through his daughter and his grandson) was hedonistic, holding pleasure to be the only good.
By far the most important disciple of Socrates, however, was Plato, a scion of one of the most noble Athenian families, who could trace his ancestry back to the last king of Athens and to Solon (c. 630–c. 560 bc), the great social and political reformer.
As a very young man, Plato became a fervent admirer of Socrates in spite of the latter’s plebeian origins. Contrary to his master, however, who always concerned himself with the attitudes of individuals, Plato believed in the importance of political institutions. In his early youth he had observed that the Athenian masses, listening to the glorious projects of ambitious politicians, had engaged in foolhardy adventures of conquest, which led in the end to total defeat in the Peloponnesian War (431–404 bc). When, in consequence of the disaster, democracy was abolished, Plato at first set great hopes in the Thirty Tyrants—especially since their leader, Critias, was a close relative. But he soon discovered that—to use his own words—the despised democracy had been gold in comparison with the new terror. When the oligarchy was overthrown and the restored democracy, in 399 bc, adopted a new law code—in fact, a kind of written constitution containing safeguards against rash political decisions—Plato again had considerable hope and was even inclined to view the execution of Socrates as an unfortunate incident rather than a logical consequence of the new regime. It was only some years later, when demagogy appeared to raise its head again, that he “despaired and was forced to say that things would not become better in politics unless the philosophers would become rulers or the rulers philosophers.” He wrote a dialogue, the Gorgias, violently denouncing political oratory and propaganda, and then traveled to southern Italy in order to study political conditions there. Again, however, he found the much-vaunted dolce vita of the Greeks there, in which the rich lived in luxury exploiting the poor, much worse than in the democracy at Athens. But at Syracuse he met a young man, Dion (c. 408–354 bc)—brother-in-law of the ruling tyrant, Dionysius I (c. 430–367 bc)—who listened eagerly to his political ideas and promised to work for their realization if any occasion should arise. On his return to Athens, Plato founded the Academy, an institution for the education of philosophers, and in the following years he produced, besides other dialogues, his great work, Republic, in which he drew the outlines of an ideal state. Because it is the passions and desires of human beings that cause all disturbances in society, the state must be ruled by an elite that governs exclusively by reason and is supported by a class of warriors entirely obedient to it.
Both ruling classes must have no individual possessions and no families and lead an extremely austere life, receiving the necessities of life from the working population, which alone is permitted to own private property. The elite receives a rigid education to fit it for its task. At the death of Dionysius, Dion induced Plato to come to Syracuse again to try to persuade Dionysius’s successor, Dionysius II (flourished 4th century bc), to renounce his power in favour of a realization of Plato’s ideals. But the attempt failed, and in his later political works, the Statesman and the Laws, Plato tried to show that only a god could be entrusted with the absolute powers of the philosopher-rulers of his republic. Human rulers must be controlled by rigid laws, he held—though all laws are inevitably imperfect because life is too varied to be governed adequately by general rules. But the Laws still placed strict restrictions on the ownership of property.
In the field of theoretical philosophy, Plato’s most influential contribution was undoubtedly his theory of Forms, which he derived from Socrates’ method in the following way: Socrates, in trying to bring out the inconsistencies in his interlocutors’ opinions and actions, often asked what it is that makes people say that a certain thing or action is good or beautiful or pious or brave; and he asked what people are looking at when they make such statements. Plato sometimes, in his dialogues, made Socrates ask what is the eidos, or idea—i.e., the image—that a person has before him when he calls something “good.” A definite answer is never given, however, because no abstract definition would be adequate, the purpose being rather to make the interlocutor aware of the fact that he somehow does look at something indefinable when making such statements.
What was at first simply a way of somehow expressing something that is difficult to express developed into a definite theory of Forms when Plato made the discovery that something similar could be observed in the field of mathematics. No two things in the visible world are perfectly equal, just as there is nothing that is perfectly good or perfectly beautiful. Yet equality is one of the most fundamental concepts not only in mathematics but also in everyday life—the foundation of all measurement. Hence, like the notion of the good and the beautiful, it appears to come from a different world, a world beyond the senses, a world that Plato then called the world of Forms. Further intimations of such a realm beyond the immediate realm of the senses may be found in the fact that, in construing a system of knowledge, people constantly prefer what is more perfect to what is less perfect—i.e., what is formed and thus recognizable to what is not, what is true to what is false, a sound logical conclusion to a logical fallacy, even an elegant scientific demonstration to a clumsy one, without considering the former as good and the latter as bad.
According to Plato, all of the things that people perceive with their senses are but very imperfect copies of the eternal Forms. The most important and fundamental Form is that of the Good. It is “beyond being and knowledge,” yet it is the foundation of both. “Being” in this context does not mean existence, but something specific—a human, a lion, or a house—being recognizable by its quality or shape.
Knowledge begins with a perception of these earthly shapes, but it ascends from there to the higher realm of Forms, which is approachable to the human mind. In the famous myth of the cave in the seventh book of the Republic, Plato likened the ordinary person to a man sitting in a cave looking at a wall on which he sees nothing but the shadows of real things behind his back, and he likened the philosopher to a man who has gotten out into the open and seen the real world of the Forms. Coming back, he may be less able to distinguish the shades because he has been blinded by the light outside; but he is the only one who knows reality, and he conducts his life accordingly.
In his later dialogues, especially the Theaetetus, Plato criticized an empiricist theory of knowledge, anticipating the views of 17th-century English philosophers such as Thomas Hobbes (1588–1679). In the Timaeus, Plato tried to construct a complete system of physics, partly employing Pythagorean ideas.
After Plato’s death, the Academy continued to exist for many centuries under various heads. When Plato’s nephew, Speusippus (died c. 338 bc), was elected as his successor, Plato’s greatest disciple, Aristotle (384–322 bc), left for Assus, a Greek city-state in Anatolia, and then went to the island of Lesbos. But soon thereafter he was called to the Macedonian court at Pella to become the educator of the crown prince, who later became Alexander the Great (356–323 bc). After Alexander became king, Aristotle returned to Athens and opened there a school of his own, the Lyceum, whose members were known as Peripatetics.
Aristotle became a member of the Academy at the age of 17, in the year 367 bc, when the school was under the acting chairmanship of Eudoxus of Cnidus (c. 395–c. 342 bc), a great mathematician and geographer (Plato was away in Sicily at the time). It is a controversial question as to how far Aristotle, during the 20 years of his membership in the Academy, developed a philosophy of his own differing from that of his master. But two things can be considered as certain: (1) that he soon raised certain objections to Plato’s theory of Forms, for one of the objections attributed to him is discussed in Plato’s dialogue Parmenides, which Plato must have written soon after his return from Sicily, and (2) that it was during his membership in the Academy that Aristotle began and elaborated his theoretical and formal analysis of the arguments used in various Socratic discussions—an enterprise that, when completed, resulted in the corpus of his works on logic. Aristotle rightly claimed to have invented this discipline; indeed, until rather recent times it was said that he completed it in such a way that hardly anything could be added.
Certainly quite some time before his return to Athens to open a school of his own, Aristotle declared that it is not necessary to assume the existence of a separate realm of transcendent Forms, of which the individual things that human beings perceive with their senses are but imperfect copies; that the world of perceived things is the real world; and that, in order to build up a system of knowledge about certain types or groups of things, it is necessary merely to be able to say that something is generally true of them. Thus, it would be wrong to say that, having abandoned the theory of Forms, Aristotle was left with a completely contingent world. The last chapters of his Posterior Analytics show, on the contrary, that he merely replaced Plato’s transcendent Forms with something (katholou) corresponding to them that the human mind can grasp in individual things.
Aristotle retained another important element of the theory of Forms in his teleology, or doctrine of purposiveness. According to Plato, individual things are imperfect copies of perfect Forms. Aristotle pointed out, however, that all living beings develop from an imperfect state (from the seed, the semen, through the germinating plant, or embryo, to the child and young adult) to the more perfect state of the fully developed plant or the full-grown mature animal or human—after which they again decay and finally die, having reproduced. But not all individuals reach the same degree of relative perfection. Many of them die before reaching it; others are retarded or crippled or maimed in various ways in the process. It is, therefore, of the utmost importance for human beings to find out what the best conditions are for reaching the most perfect state possible. This is what the gardener tries to do for the plants; but it is even more important for humankind to do in regard to itself. The first question, then, is what kind of perfection a human being, as human, can reach. In answering this question, Aristotle observed that human beings, as social animals par excellence, can reach as individuals only some of the perfections possible for humans as such. Cats are more or less all alike in their functions; thus each can fend for itself. With bees and termites, however, it is different. They are by nature divided into worker bees, drones, and queen bees, or worker termites, soldier termites, and queens. With human beings the differentiation of functions is much more subtle and varied. People can lead satisfactory lives only on the basis of a division of labour and distribution of functions. Some individuals are born with very great talents and inclinations for special kinds of activity. They will be happy and will make their best possible contribution to the life of the community only if they are permitted to follow this inclination. Others are less one-sidedly gifted and more easily adaptable to a variety of functions. These people can be happy shifting from one activity to another. This fact represents an enormous advantage the human species has over all other animals, because it enables it to adapt to all sorts of circumstances. But the advantage is paid for by the fact that no human individual is able to develop all of the perfections that are possible for the species as a whole.
There is another possible and, in its consequences, real disadvantage to such adaptability: the other animals, tightly confined to the limits set by nature, are crippled almost exclusively by external factors, but humans, in consequence of the freedom of choice granted to them through the variety of their gifts, can and very often do cripple and harm themselves. All human activities are directed toward the end of a good and satisfactory life. But there are many subordinate aims that are sensible ends only as far as they serve a superior end. There is, for example, no sense in producing or acquiring more shoes than can possibly be worn. This is self-evident. With regard to money, however, which has become exchangeable against everything, the illusion arises that it is good to accumulate it without limit. By doing so, humans harm both the community and themselves because, by concentrating on such a narrow aim, they deprive their souls and spirits of larger and more rewarding experiences.
Similarly, an individual especially gifted for large-scale planning needs power to give orders to those capable of executing his plans. Used for such purposes, power is good. But coveted for its own sake, it becomes oppressive to those subdued by it and harmful to the oppressor because he thus incurs the hatred of the oppressed. Because of their imperfections, humans are not able to engage in serious and fruitful activities without interruption. They need relaxation and play, or amusement. Because the necessities of life frequently force them to work beyond the limit within which working is pleasant, the illusion arises that a life of constant amusement would be the most pleasant and joyful. In reality nothing would be more tedious.
Aristotle’s teleology seems to be based entirely on empirical observation. It has nothing to do with a belief in divine providence and is not, as some modern critics believe, at variance with the law of causality. It forms the foundation, however, of Aristotle’s ethics and political theory. Aristotle was an avid collector of empirical evidence. He induced his students, for instance, to study the laws and political institutions of all known cities and nations in order to find out how they worked and at what points their initiators had been mistaken regarding the way in which they would work. In later times, Aristotle came to be considered (and by many is still considered) a dogmatic philosopher because the results of his inquiries were accepted as absolutely authoritative. In reality, however, he was one of the greatest empiricists of all times.
Disciples and commentators
After Aristotle’s death his immediate disciples carried on the same kind of work, especially in the historical field: Theophrastus wrote a history of philosophy and works on botany and mineralogy, Eudemus of Rhodes (flourished before 300 bc) wrote histories of mathematics and astronomy, Meno wrote a history of medicine, and Dicaearchus of Messene (flourished c. 320 bc) wrote a history of civilization and a book on types of political constitutions. The next two generations of Peripatetics spread out in two directions: literary history, in the form of histories of poetry, epic, tragedy, and comedy, as well as biographies of famous writers, and physical science. Straton of Lampsacus (died c. 270 bc) created a new kind of physics based on experiments, and the great astronomer Aristarchus of Samos (c. 310–230 bc) invented the heliocentric system. The school then went for some time into eclipse until, in the 1st century ad, after the rediscovery of Aristotle’s lecture manuscripts, there arose a great school of commentators on his works, which had an enormous influence on medieval philosophy.
Hellenistic and Roman philosophy
The period after the death of Aristotle was characterized by the decay of the Greek city-states, which then became pawns in the power game of the Hellenistic kings who succeeded Alexander. Life became troubled and insecure. It was in this environment that two dogmatic philosophical systems came into being, Stoicism and Epicureanism, which promised to give their adherents something to hold onto and to make them independent of the external world.
The Stoic system was created by a Syrian, Zeno of Citium (c. 335–c. 263 bc), who went to Athens as a merchant but lost his fortune at sea. Zeno was consoled by the Cynic philosopher Crates of Thebes (flourished 4th century bc), who taught him that material possessions were of no importance whatever for a person’s happiness. He therefore stayed at Athens, heard the lectures of various philosophers, and—after he had elaborated his own philosophy—began to teach in a public hall, the Stoa Poikile (hence the name Stoicism).
Zeno’s thought comprised, essentially, a dogmatized Socratic philosophy, with added ingredients derived from Heracleitus (c. 540–c. 480 bc). The basis of human happiness, he said, is to live “in agreement” with oneself, a statement that was later replaced by the formula “to live in agreement with nature.” The only real good for a human being is the possession of virtue; everything else—wealth or poverty, health or illness, life or death—is completely indifferent. All virtues are based exclusively on right knowledge, self-control (sōphrosynē) being the knowledge of the right choice, fortitude the knowledge of what must be endured and what must not, and justice the right knowledge “in distribution.” The passions, which are the cause of all evil, are the result of error in judging what is a real good and what is not. Because it is difficult to see, however, why murder, fraud, and theft should be considered evil if life and possessions are of no value, the doctrine was later modified to distinguish between “preferable things,” such as having the necessities of life and health, “completely indifferent things,” and “anti-preferable things,” such as lacking the necessities of life or health—while insisting still that the happiness of the truly wise person could not be impaired by illness, pain, hunger, or any deprivation of external goods. In the beginning, Zeno also insisted that an individual is either completely wise, in which case he would never do anything wrong and would be completely happy, or he is a fool. Later he made the concession, however, that there are people who are not completely wise but who are progressing toward wisdom. Although these people might even have true insight, they are not certain that they have it, whereas the truly wise person is also certain of having true insight. The world is governed by divine logos—a word originally meaning “word” or “speech,” then (with Heracleitus) a speech that expresses the laws of the universe, then (finally) “reason.” This logos keeps the world in perfect order. Human beings can deviate from or rebel against this order, but, by doing so, they cannot disturb it but can only do harm to themselves.
Zeno’s philosophy was further developed by Cleanthes (c. 331–c. 232 bc), the second head of the school, and by Chrysippus (c. 280–c. 206 bc), its third head. Chrysippus elaborated a new kind of logic, which did not receive much attention outside the Stoic school until recent times; this “propositional logic” has been hailed by some logicians as superior to the “conceptual logic” of Aristotle. Panaetius of Rhodes (c. 180–109 bc) adapted Stoic philosophy to the needs of the Roman aristocracy, whose members then governed the Western world, and made a great impression on some of the leading figures of the time, who tried to follow his moral precepts. In the following century, a time of civil war, slave rebellions, and the decay of the Roman Republic, Poseidonius of Apamea (c. 135–c. 51 bc), who was also one of the most brilliant historians of all times, taught that the Stoic takes a position above the rest of humankind, looking down on its struggles as on a spectacle. In the period of the consolidation of the empire, Stoicism became the religion of the republican opposition. The most famous Stoic was the younger Cato (95–46 bc), who committed suicide after the victory of Julius Caesar (c. 100–44 bc). It was also the guiding philosophy of Seneca the Younger (c. 4 bc–ad 65), the educator and (for a long time) the adviser of the emperor Nero (37–68), who tried to keep Nero on the path of virtue but failed and finally was forced to commit suicide on Nero’s orders. Despite the oddities of Zeno’s original doctrine, Stoicism gave consolation, composure, and fortitude in times of trouble to many proud individuals to the end of antiquity and beyond.
The thought of Zeno’s contemporary Epicurus (341–270 bc) also constituted a philosophy of defense in a troubled world. Nevertheless, it has been considered—in many respects justly—the opposite of Zeno’s thought. Whereas Zeno proclaimed that the wise person tries to learn from everybody and always acknowledges his debt to earlier thinkers, Epicurus insisted that everything he taught was original to himself, though it is obvious that his physical explanation of the universe is a simplification of Democritus’s atomism. And whereas the Stoics had taught that pleasure and pain are of no importance for a person’s happiness, Epicurus made pleasure the very essence of a happy life. Moreover, the Stoics from the beginning had acted as advisers of kings and statesmen. Epicurus, on the other hand, lived in the retirement of his famous garden, cultivating intimate friendships with his adherents but warning against participation in public life. The Stoics believed in divine providence; Epicurus taught that the gods pay no attention whatever to human beings. Yet despite these contrasts, the two philosophies had some essential features in common. Although Epicurus made pleasure the criterion of a good life, he was far from advocating dissolution and debauchery; he insisted that it is the simple pleasures that make a life happy. When, in his old age, he suffered terrible pain from prostatitis, he asserted that philosophizing and the memory and love of his distant friends made pleasure prevail even then. Nor was Epicurus an atheist. His Roman admirer, the poet Lucretius (flourished 1st century bc), in his poem De rerum natura (On the Nature of Things), praised Epicurus enthusiastically as the liberator of humankind from all religious fears; Epicurus himself affirmed that this had been one of the aims of his philosophy. But although he taught that the gods are much too superior to trouble themselves with the affairs of mortals, he said—and, as his language clearly shows, sincerely believed—that it is important for human beings to look at the gods as perfect, since only in this way could humans approach perfection. It was only in Roman times that people began to misunderstand Epicureanism, holding it to be an atheistic philosophy justifying a dissolute life, so that a person could be called “a swine from the herd of Epicurus.” Seneca, however, recognized the true nature of Epicureanism; in his Epistulae morales (Moral Letters) he deliberately interspersed maxims from Epicurus through his Stoic exhortations.
There was still another Hellenistic school of philosophy, Skepticism, which was initiated by another of Zeno’s contemporaries, Pyrrhon of Elis (c. 360–c. 272 bc), and was destined to become of great importance for the preservation of detailed knowledge of Hellenistic philosophy in general. Pyrrhon had come to the conviction that no one can know anything for certain, nor can he ever be certain that the things he perceives with his senses are real and not illusory. Pyrrhon is said to have carried the practical consequences of his conviction so far that, when walking in the streets, he paid no attention to vehicles and other obstacles, so that his faithful disciples always had to accompany him to see that he came to no harm. Pyrrhon’s importance for the history of philosophy lies in the fact that one of the later adherents of his doctrine, Sextus Empiricus (flourished 3rd century ad), wrote a large work, Pros dogmatikous (“Against the Dogmatists”), in which he tried to refute all of the philosophers who held positive views, and in so doing he quoted extensively from their works, thus preserving much that would otherwise have been lost. It is a noteworthy fact that the British empiricists of the 18th century, such as David Hume (1711–76), as well as Immanuel Kant (1724–1804), derived most of their knowledge of ancient philosophy from Sextus Empiricus.
Neo-Pythagoreanism and Neoplatonism
All of the philosophical schools and sects of Athens that originated in the 4th century bc continued into late antiquity, most of them until the emperor Justinian I (ad 483–565) ordered them closed in 529 because of their pagan character. Within this period of nearly 1,000 years, only two new schools emerged, neo-Pythagoreanism and Neoplatonism; both were inspired by early Greek philosophy, though only the latter would become historically important. Neoplatonism was established by Ammonius Saccas (fl. early 3rd century ad), who had been brought up as a Christian but had abandoned his religion for the study of Plato. Because Ammonius wrote nothing, his philosophy is known only through his famous disciple, Plotinus (205–270). But Plotinus did not publish anything either. His philosophy is known through the Enneads, a collection of his writings arranged by his disciple Porphyry (234–305), who also wrote a biography of Plotinus.
Although the philosophy of Plotinus (and Ammonius) was derived from Plato, it used many philosophical terms first coined by Aristotle and adopted some elements of Stoicism as well. Yet it was essentially a new philosophy, agreeing with the religious and mystical tendencies of its time. Plotinus assumed the existence of several levels of Being, the highest of which is that of the One or the Good, which are identical but indescribable and indefinable in human language. The next lower level is that of nous, or pure intellect or reason; the third is that of the soul or souls. There then follows the world perceived by the senses. Finally, at the lowest level there is matter, which is the cause of all evil. The highest bliss available to human beings is union with the One, or the Good, which is attained by contemplation and purification. That this is not a lasting state attained once and for all—like the status of the Stoic wise man, who was supposed never to lose his wisdom—is shown by the fact that Porphyry, in his biography, said that Plotinus had experienced this supreme bliss seven times in his life, whereas he, Porphyry, had experienced it only once.
The further history of Neoplatonism is extremely complicated. While Porphyry had emphasized the ethical element in Plotinus’s philosophy, his disciple in Syria, Iamblichus of Chalcis (c. 250–c. 330), mingled Neoplatonism with neo-Pythagoreanism, writing on the Pythagorean way of life and on number theory. Above all, he multiplied the levels of Being, or the emanations from the One, which enabled him to incorporate the traditional Greek gods into his system. Another branch of the school was founded in Pergamum, in western Asia Minor, by Iamblichus’s student Aedesius (died 355), who, with his own disciple Maximus of Ephesus (died 370), tried to revive the ancient Greek mystery religions, such as Orphism (see mystery religion). All of these developments became of great importance in the 4th century, when Emperor Julian the Apostate (c. 331–363) attempted to revive paganism. In the following century the Athenian school reached a new high point when Proclus (c. 410–485) combined the ideas of his predecessors into a comprehensive system. When Justinian closed all of the philosophical schools in Athens in 529, however, a branch continued to exist in Alexandria. The Athenian Neoplatonists found refuge at the court of the Persian king Khosrow I (died 579), and in 535 they were permitted to return to Athens. But gradually pagan philosophy as such died out, though it continued to influence the development of Christian philosophy and theology.
Medieval philosophy
Medieval philosophy designates the philosophical speculation that occurred in western Europe during the Middle Ages—i.e., from the fall of the Roman Empire in the 4th and 5th centuries ad to the Renaissance of the 15th century. Philosophy of the medieval period was closely connected to Christian thought, particularly theology, and the chief philosophers of the period were churchmen. Philosophers who strayed from this close relation were chided by their superiors. Greek philosophy ceased to be creative after Plotinus in the 3rd century ad. A century later, Christian thinkers such as St. Ambrose (339–397), St. Victorinus (died c. 304), and St. Augustine (354–430) began to assimilate Neoplatonism into Christian doctrine in order to give a rational interpretation of Christian faith. Thus, medieval philosophy was born of the confluence of Greek (and to a lesser extent of Roman) philosophy and Christianity. Plotinus’s philosophy was already deeply religious, having come under the influence of Middle Eastern religions. Medieval philosophy continued to be characterized by this religious orientation. Its methods were at first those of Plotinus and later those of Aristotle. But it developed within faith as a means of throwing light on the truths and mysteries of faith. Thus, religion and philosophy fruitfully cooperated in the Middle Ages. Philosophy, as the handmaiden of theology, made possible a rational understanding of faith. Faith, for its part, inspired Christian thinkers to develop new philosophical ideas, some of which became part of the philosophical heritage of the West.
Toward the end of the Middle Ages, this beneficial interplay of faith and reason started to break down. Philosophy began to be cultivated for its own sake, apart from—and even in contradiction to—Christian religion. This divorce of reason from faith, made definitive in the 17th century by Francis Bacon (1561–1626) in England and René Descartes (1596–1650) in France, marked the birth of modern philosophy.
The early Middle Ages
The early medieval period, which extended to the 12th century, was marked by the barbarian invasions of the Western Roman Empire, the collapse of its civilization, and the gradual building of a new, Christian culture in western Europe. Philosophy in these dark and troubled times was cultivated by late Roman thinkers such as Augustine and Boethius (c. 470–524), then by monks such as St. Anselm of Canterbury (c. 1033–1109). The monasteries became the main centres of learning and education and retained their preeminence until the founding of the cathedral schools and universities in the 11th and 12th centuries.
During these centuries philosophy was heavily influenced by Neoplatonism; Stoicism and Aristotelianism played only a minor role. Augustine was awakened to the philosophical life by reading the Roman statesman Cicero (106–43 bc), but the Neoplatonists most decisively shaped his philosophical methods and ideas. To them he owed his conviction that beyond the world of the senses there is a spiritual, eternal realm of Truth that is the object of the human mind and the goal of all human striving. This Truth he identified with the God of Christianity. Human beings encounter this divine world not through the senses but through the mind—and, above the mind, through the intelligible light. Augustine’s demonstration of the existence of God coincides with his proof of the existence of necessary, immutable Truth. He considered the truths of both mathematics and ethics to be necessary, immutable, and eternal. These truths cannot come from the world of contingent, mutable, and temporal things, nor from the mind itself, which is also contingent, mutable, and temporal. They are due to the illuminating presence in the human mind of eternal and immutable Truth, or God. Any doubt that humans may know the Truth with certainty was dispelled for Augustine by the certitude that, even if they are deceived in many cases, they cannot doubt that they exist, know, and love.
Augustine conceived of human beings as composites of two substances, body and soul, of which the soul is by far the superior. The body, nevertheless, is not to be excluded from human nature, and its eventual resurrection from the dead is assured by Christian faith. The soul’s immortality is proved by its possession of eternal and unchangeable Truth.
Augustine’s Confessions (c. 400) and De Trinitate (400–416; On the Trinity) abound with penetrating psychological analyses of knowledge, perception, memory, and love. His De civitate Dei (413–426; The City of God) presents the whole drama of human history as a progressive movement of humankind, redeemed by God, to its final repose in its Creator.
One of the most important channels by which Greek philosophy was transmitted to the Middle Ages was Boethius. He began to translate into Latin all the philosophical works of the Greeks, but his imprisonment and death by order of Theodoric, king of the Ostrogoths, cut short this project. He finished translating only the logical writings of Porphyry and Aristotle. These translations and his commentaries on them brought to the thinkers of the Middle Ages the rudiments of Aristotelian logic. They also raised important philosophical questions, such as those concerning the nature of universals (terms that can be applied to more than one particular thing). Do universals exist independently, or are they only mental concepts? If they exist independently, are they corporeal or incorporeal? If incorporeal, do they exist in the sensible world or apart from it? Medieval philosophers debated at length these and other problems relating to universals. In his logical works Boethius presents the Aristotelian doctrine of universals: that they are only mental abstractions. In his De consolatione philosophiae (c. 525; Consolation of Philosophy), however, he adopts the Platonic notion that they are innate ideas, and their origin is in the remembering of knowledge from a previous existence. This book was extremely popular and influential in the Middle Ages. It contains not only a Platonic view of knowledge and reality but also a lively treatment of providence, divine foreknowledge, chance, fate, and human happiness.
The Greek Fathers of The Church and Erigena
Another stream from which Greek philosophy, especially Neoplatonic thought, flowed into the Middle Ages was the Greek Fathers of the Church, notably Origen (c. 185–c. 254), St. Gregory of Nyssa (c. 335–c. 394), Nemesius of Emesa (flourished 4th century), Pseudo-Dionysius the Areopagite (flourished c. 500), and St. Maximus the Confessor (c. 580–662). In the 9th century John Scotus (810–c. 877), called Erigena (“Belonging to the People of Erin”) because he was born in Ireland, a master at the Carolingian court of Charles II the Bald (823–877), translated into Latin some of the writings of these Greek theologians, and his own major work, De divisione naturae (862–866; On the Division of Nature), is a vast synthesis of Christian thought organized along Neoplatonic lines. For Scotus, God is the primal unity, unknowable and unnameable in himself, from which the multiplicity of creatures flows. He so far transcends his creatures that he is most appropriately called superreal and supergood. Creation is the process of division whereby the many derive from the One. The One descends into the manifold of creation and reveals himself in it. By the reverse process, the multiplicity of creatures will return to their unitary source at the end of time, when everything will be absorbed in God.
Although the Carolingian empire collapsed in the 10th century and intellectual speculation was at a low ebb in western Europe, signs of revival appeared almost contemporaneously. Political stability was achieved by Otto I, who reestablished the empire in 963, and Benedictine monasteries were revitalized by reform movements begun at Cluny and Gorze. In the next century, reformers such as Peter Damian combined the ascetic and monastic traditions and laid the foundation for the vita apostolica. Like Tertullian, a Christian writer of the 2nd and 3rd centuries, Damian mistrusted secular learning and philosophy as harmful to the faith. Other monks showed a keen interest in dialectic and philosophy. Among the latter was Anselm, an Italian who became abbot of the French monastery of Bec and later archbishop of Canterbury.
Like Augustine, Anselm used both faith and reason in his search for truth. Faith comes first, in his view, but reason should follow, giving reasons for what human beings believe. Anselm’s monks asked him to write a model meditation on God in which everything would be proved by reason and nothing on the authority of Scripture. He replied with his Monologium (1077; “Monologue”). It contains three proofs of the existence of God, all of which are based on Neoplatonic thought. The first proof moves from the awareness of a multiplicity of good things to the recognition that they all share or participate more or less in one and the same Good, which is supremely good in itself, and this is God. The second and third proofs are similar, moving from an awareness of a multiplicity of beings that are more or less perfect to the recognition of that through which everything exists, which itself is supremely perfect.
Anselm’s later work, the Proslogium (1077/78; “Allocution” or “Address”), contains his most famous proof of the existence of God. This begins with a datum of faith: humans believe God to be the being than which none greater can be conceived. Some, like the fool in the Psalms, say there is no God; but even the fool, on hearing these words, understands them, and what he understands exists in his intellect, even though he does not grant that such a being exists in reality. But it is greater to exist in reality and in the understanding than to exist in the understanding alone. Therefore it is contradictory to hold that God exists only in the intellect, for then the being than which none greater can be conceived is one than which a greater can be conceived—namely, one that exists both in reality and in the understanding. Philosophers still debate the meaning and value of this so-called ontological argument for God’s existence.
Bernard De Clairvaux and Abelard
Anselm’s inquiry into the existence and nature of God, as also his discussion of truth, love, and human liberty, aimed at fostering monastic contemplation. Other monks, such as the Cistercian St. Bernard de Clairvaux (1090–1153), were suspicious of the use of secular learning and philosophy in matters of faith. Bernard complained of the excessive indulgence in dialectic displayed by contemporaries such as Peter Abelard (1079–1142). He himself developed a doctrine of mystical love, the influence of which lasted for centuries. The monks of the Parisian abbey of Saint-Victor were no less intent on fostering mystical contemplation, but they cultivated the liberal arts and philosophy as an aid to it. In this spirit, Hugh of Saint-Victor (1096–1141) wrote his Didascalicon (c. 1127; “Teaching”; Eng. trans., Didascalicon), a monumental treatise on the theoretical and practical sciences and on the trivium (grammar, rhetoric, dialectic) and the quadrivium (arithmetic, music, geometry, astronomy). During the same period the School of Chartres, attached to the famous Chartres Cathedral near Paris, was the focus of Christian Neoplatonism and humanism.
Urban development in the 12th century shifted the centre of learning and education from the monasteries to the towns. Abelard founded and taught in several urban schools near Paris. A passionate logician, he pioneered a method in theology that contributed to the later Scholastic method. His Sic et non (1115–17; Yes and No) cites the best authorities on both sides of theological questions in order to reach their correct solution. In philosophy his main interest was logic. On the question of universals, he agreed with neither the nominalists nor the realists of his day (see nominalism and realism). His nominalist teacher Roscelin (c. 1050–c. 1125) held that universals, such as “man” and “animal,” are nothing but words, or names (flatus vocis). Abelard argued that this does not take into account the fact that names have meaning. His realist teacher William of Champeaux (c. 1070–1121) taught that universals are realities apart from the mind. For Abelard, only individuals are real; universals are indeed names or mental concepts, but they have meaning because they refer to individuals. They do not signify an essence common to individuals, as the realists maintained (e.g., the essence “humanity” shared by all human beings), but signify instead the individuals in their common condition, or status, of being in a certain species, which results from God having created them according to the same divine idea.
The transition to Scholasticism
In the 12th century a cultural revolution took place that influenced the entire subsequent history of Western philosophy. The old style of education, based on the liberal arts and emphasizing grammar and the reading of the Latin classics, was replaced by new methods stressing logic, dialectic, and all the scientific disciplines known at the time. John of Salisbury (c. 1115–1180), of the School of Chartres, witnessed this radical change:
Behold, everything was being renovated: grammar was being made over, logic was being remodeled, rhetoric was being despised. Discarding the rules of their predecessors, [the masters] were teaching the quadrivium with new methods taken from the very depths of philosophy.
In philosophy itself, there was a decline in Platonism and a growing interest in Aristotelianism. This change was occasioned by the translation into Latin of the works of Aristotle in the late 12th and the early 13th century. Until then, only a few of his minor logical treatises were known. Now his Topica, Analytica priora, and Analytica posteriora were rendered into Latin, giving the Schoolmen access to the Aristotelian methods of disputation and science, which became their own techniques of discussion and inquiry. Many other philosophical and scientific works of Greek and Arabic origin were translated at this time, creating a “knowledge explosion” in western Europe.
Arabic Thought
Among the works to be translated from Arabic were some of the writings of Avicenna (980–1037). This Islamic philosopher had an extraordinary impact on the medieval Schoolmen. His interpretation of Aristotle’s notion of metaphysics as the science of ens qua ens (Latin: “being as being”), his analysis of many metaphysical terms, such as being, essence, and existence, and his metaphysical proof of the existence of God were often quoted, with approval or disapproval, in Christian circles. Also influential were his psychology, logic, and natural philosophy. His Al-Qānūn fī al-ṭibb (Canon of Medicine) was authoritative on the subject until modern times. The Maqāṣid al-falāsifah (1094; “The Aims of the Philosophers”) of the Arabic theologian al-Ghazālī (1058–1111; known in Latin as Algazel), an exposition of Avicenna’s philosophy written in order to criticize it, was read as a complement to Avicenna’s works. The anonymous Liber de causis (“Book of Causes”) was also translated into Latin from Arabic. This work, excerpted from Proclus’s Stiocheiōsis theologikē (Elements of Theology), was often ascribed to Aristotle, and it gave a Neoplatonic cast to his philosophy until its true origin was discovered by St. Thomas Aquinas (c. 1224–1274).
The commentaries of the Arabic philosopher Averroës (1126–98) were translated along with Aristotle’s works. As Aristotle was called “the Philosopher” by the medieval philosophers, Averroës was dubbed “the Commentator.” The Christian Schoolmen often attacked Averroës as the archenemy of Christianity for his rationalism and his doctrine of the eternity of the world and the unity of the intellect for all human beings—i.e., the doctrine that intellect is a single, undifferentiated form with which individuals become reunited at death. This was anathema to the Christian Schoolmen because it contravened the Christian doctrine of individual immortality.
Jewish Thought
Of considerably less influence on the Scholastics was medieval Jewish thought. Ibn Gabirol (c. 1022–c. 1058), known to the Scholastics as Avicebron or Avencebrol, was thought to be an Arab or Christian, though in fact he was a Spanish Jew. His chief philosophical work, written in Arabic and preserved in toto only in a Latin translation titled Fons vitae (c. 1050; The Fountain of Life), stresses the unity and simplicity of God. All creatures are composed of form and matter, either the gross corporeal matter of the sensible world or the spiritual matter of angels and human souls. Some of the Schoolmen were attracted to the notion of spiritual matter and also to Ibn Gabirol’s analysis of a plurality of forms in creatures, according to which every corporeal being receives a variety of forms by which it is given its place in the hierarchy of being—for example, a dog has the forms of a corporeal thing, a living thing, an animal, and a dog.
Moses Maimonides (1135–1204), or Moses ben Maimon, was known to Christians of the Middle Ages as Rabbi Moses. His Dalālat al-hāʾirīn (c. 1190; The Guide for the Perplexed) helped them to reconcile Greek philosophy with revealed religion. For Maimonides there could be no conflict between reason and faith because both come from God; an apparent contradiction is due to a misinterpretation of either the Bible or the philosophers. Thus, he showed that creation is reconcilable with philosophical principles and that the Aristotelian arguments for an eternal world are not conclusive because they ignore the omnipotence of God, who can create a world of either finite or infinite duration.
While Western scholars were assimilating the new treasures of Greek, Islamic, and Jewish thought, universities that became the centres of Scholasticism were being founded. Of these, the most important were located in Paris and Oxford (formed 1150–70 and 1168, respectively). Scholasticism is the name given to the theological and philosophical teachings of the Schoolmen in the universities. There was no single Scholastic doctrine; each of the Scholastics developed his own, which was often in disagreement with that of his fellow teachers. They had in common a respect for the great writers of old, such as the Fathers of the Church, Aristotle, Plato, Boethius, Pseudo-Dionysius, and Avicenna. These they called “authorities.” Their interpretation and evaluation of the authorities, however, frequently differed. They also shared a common style and method that developed out of the teaching practices in the universities. Teaching was done by lecture and disputation (a formal debate). A lecture consisted of the reading of a prescribed text followed by the teacher’s commentary on it. Masters also held disputations in which the affirmative and negative sides of a question were thoroughly argued by students and teacher before the latter resolved the problem.

The age of the Schoolmen

Robert Grosseteste and Roger Bacon
The newly translated Greek and Arabic treatises had an immediate effect on the University of Oxford. Its first chancellor, Robert Grosseteste (c. 1175–1253), commented on some of Aristotle’s works and translated the Nicomachean Ethics from Greek to Latin. He was deeply interested in scientific method, which he described as both inductive and deductive. By the observation of individual events in nature, human beings advance to a general law, called a “universal experimental principle,” which accounts for these events. Experimentation either verifies or falsifies a theory by testing its empirical consequences. For Grosseteste, the study of nature is impossible without mathematics. He cultivated the science of optics (perspectiva), which measures the behaviour of light by mathematical means. His studies of the rainbow and comets employ both observation and mathematics. His treatise De luce (1215–20; On Light) presents light as the basic form of all things and God as the primal, uncreated light.
Grosseteste’s pupil Roger Bacon (c. 1220–1292) made the mathematical and experimental methods the key to natural science. The term experimental science was popularized in the West through his writings. For him, human beings acquire knowledge through reasoning and experience, but without the latter there can be no certitude. Humans gain experience through the senses and also through an interior divine illumination that culminates in mystical experience. Bacon was critical of the methods of Parisian theologians such as St. Albertus Magnus (c. 1200–1280) and Aquinas. He strove to create a universal wisdom embracing all the sciences and organized by theology. He also proposed the formation of a single worldwide society, or “Christian republic,” that would unite all humankind under the leadership of the pope.
William of Auvergne
At the University of Paris, William of Auvergne (c. 1180–1249) was one of the first to feel the impact of the philosophies of Aristotle and Avicenna. As a teacher and then as bishop of Paris, he was concerned with the threat to the Christian faith posed by pagan and Islamic thought. He opposed the Aristotelian doctrine of the eternity of the world as contrary to the Christian notion of creation. His critique of Avicenna emphasized the latter’s conception of God and creation. Against the God of Avicenna, who creates the universe eternally and necessarily through the mediation of 10 intelligences, William defended the Christian notion of a God who creates the world freely and directly. Creatures are radically contingent and dependent on God’s creative will. Unlike God, they do not exist necessarily; indeed, their existence is distinct from their essence and accidental to it. God has no essence distinct from his existence; he is pure existence. In stressing the essential instability and temporality of the world, William attributed true existence and causality to God alone. Although a follower of Augustine, William, like others of his time, was compelled to rethink the older Augustinian notions in terms of the newer Aristotelian and Avicennian philosophies.
The Franciscan friar St. Bonaventure (c. 1217–1274) reacted similarly to the growing popularity of Aristotle and his Arabic commentators. He admired Aristotle as a natural scientist, but he preferred Plato and Plotinus, and above all Augustine, as metaphysicians. His main criticism of Aristotle and his followers was that they denied the existence of divine ideas. As a result, Aristotle was ignorant of exemplarism (God’s creation of the world according to ideas in his mind) and also of divine providence and government of the world. This involved Aristotle in a threefold blindness: he taught that the world is eternal, that all men share one agent intellect (the active principle of understanding), and that there are no rewards or punishments after death. Plato and Plotinus avoided these mistakes, but because they lacked Christian faith, they could not see the whole truth. For Bonaventure, faith alone enables one to avoid error in these important matters.
Bonaventure did not confuse philosophy with theology. Philosophy is knowledge of the things of nature and the soul that is innate in human beings or acquired through their own efforts, whereas theology is knowledge of heavenly things that is based on faith and divine revelation. Bonaventure, however, rejected the practical separation of philosophy from theology. Philosophy needs the guidance of faith; far from being self-sufficient, it is but a stage in a progression toward the higher knowledge that culminates in the vision of God.
For Bonaventure, every creature to some degree bears the mark of its Creator. The soul has been made in the very image of God. Thus, the universe is like a book in which the triune God is revealed. His Itinerarium mentis in Deum (1259; The Soul’s Journey into God) follows Augustine’s path to God, from the external world to the interior world of the mind and then beyond the mind from the temporal to the eternal. Throughout this journey, human beings are aided by a moral and intellectual divine illumination. The mind has been created with an innate idea of God so that, as Anselm pointed out, humans cannot think that God does not exist. In a terse reformulation of the Anselmian argument for God’s existence, Bonaventure states that if God is God, he exists.
Albertus Magnus
The achievement of the Dominican friar Albertus Magnus was of vital importance for the development of medieval philosophy. A person of immense erudition and intellectual curiosity, he was one of the first to recognize the true value of the newly translated Greco-Arabic scientific and philosophical literature. Everything he considered valuable in it he included in his encyclopaedic writings. He set out to teach this literature to his contemporaries and in particular to make the philosophy of Aristotle, whom he considered to be the greatest philosopher, understandable to them. He also proposed to write original works in order to complete what was lacking in the Aristotelian system. In no small measure, the triumph of Aristotelianism in the 13th century can be attributed to him.
Albertus’s observations and discoveries in the natural sciences advanced botany, zoology, and mineralogy. In philosophy he was less original and creative than his famous pupil Aquinas. Albertus produced a synthesis of Aristotelianism and Neoplatonism, blending together the philosophies of Aristotle, Avicenna, and Ibn Gabirol and, among Christians, Augustine and Pseudo-Dionysius.
Thomas Aquinas
Albertus Magnus’s Dominican confrere and pupil Thomas Aquinas shared his master’s great esteem for the ancient philosophers, especially Aristotle, and also for the more recent Arabic and Jewish thinkers. He welcomed truth wherever he found it and used it for the enrichment of Christian thought. For him reason and faith cannot contradict each other, because they come from the same divine source. In his day, conservative theologians and philosophers regarded Aristotle with suspicion and leaned toward the more traditional Christian Neoplatonism. Aquinas realized that their suspicion was partly due to the fact that Aristotle’s philosophy had been distorted by the Arabic commentators, so he wrote his own commentaries to show the essential soundness of Aristotle’s system and to convince his contemporaries of its value for Christian theology.
Aquinas’s own philosophical views are best expressed in his theological works, especially his Summa theologiae (1265/66–1273; Eng. trans., Summa theologiae) and Summa contra gentiles (1258–64; Summa Against the Gentiles). In these works he clearly distinguished between the domains and methods of philosophy and theology. The philosopher seeks the first causes of things, beginning with data furnished by the senses; the subject of the theologian’s inquiry is God as revealed in sacred scripture. In theology, appeal to authority carries the most weight; in philosophy, it carries the least.
Aquinas found Aristotelianism and, to a lesser extent, Platonism useful instruments for Christian thought and communication; but he transformed and deepened everything he borrowed from them. For example, he adopted Aristotle’s proof of the existence of a primary unmoved mover, but the primary mover at which Aquinas arrived is very different from that of Aristotle; it is in fact the God of Judaism and Christianity. He also adopted Aristotle’s teaching that the soul is the human being’s form and the body his matter, but for Aquinas this does not entail, as it did for the Aristotelians, the denial of the immortality of the soul or the ultimate value of the individual. Aquinas never compromised Christian doctrine by bringing it into line with the current Aristotelianism; rather, he modified and corrected the latter whenever it clashed with Christian belief. The harmony he established between Aristotelianism and Christianity was not forced but achieved by a new understanding of philosophical principles, especially the notion of being, which he conceived as the act of existing (esse). For him, God is pure being, or the act of existing.
Creatures participate in being according to their essence; for example, human beings participate in being, or the act of existing, to the extent that their humanity, or essence, permits. The fundamental distinction between God and creatures is that creatures have a real composition of essence and existence, whereas God’s essence is his existence.
A group of masters in the faculty of arts at Paris welcomed Aristotle’s philosophy and taught it in disregard of its possible opposition to the Christian faith. They wanted to be philosophers, not theologians, and to them this meant following the Aristotelian system. Because Averroës was the recognized commentator on Aristotle, they generally interpreted Aristotle’s thought in an Averroistic way. Hence, in their own day they were known as “Averroists”; today they are often called “Latin Averroists” because they taught in Latin. Their leader, Siger de Brabant (c. 1240–c. 1281), taught as rationally demonstrated certain Aristotelian doctrines that contradicted the faith, such as the eternity of the world and the oneness of the intellect. The Latin Averroists were accused of holding a “double truth”—i.e., of maintaining the existence of two contradictory truths, one commanded by faith, the other taught by reason. Although Siger never proposed philosophical conclusions contrary to faith, other members of this group upheld the right and duty of the philosopher to follow human reason to its natural conclusions, even when they contradicted the truths of faith.
This growing rationalism confirmed the belief of theologians of a traditionalist cast that the pagan and Islamic philosophies would destroy the Christian faith. They attacked these philosophies in treatises such as Errores philosophorum (1270; The Errors of the Philosophers) by Giles of Rome (c. 1243–1316). In 1277 the bishop of Paris condemned 219 propositions based on the new trend toward rationalism and naturalism. These included even some of Aquinas’s Aristotelian doctrines. In the same year, the archbishop of Canterbury made a similar condemnation at Oxford. These reactions to the novel trends in philosophy did not prevent the Averroists from treating philosophical questions apart from religious considerations. Theologians, for their part, were increasingly suspicious of the philosophers and less optimistic about the ultimate reconciliation of philosophy and theology.
The late Middle Ages
In the late Middle Ages earlier ways of philosophizing were continued and formalized into distinct schools of thought. In the Dominican order, Thomism, the theological and philosophical system of Thomas Aquinas, was made the official teaching, though the Dominicans did not always adhere to it rigorously. Averroism, cultivated by philosophers such as John of Jandun (c. 1286–1328), remained a significant, though sterile, movement into the Renaissance. In the Franciscan order, John Duns Scotus (c. 1266–1308) and William of Ockham (c. 1285–c. 1347) developed new styles of theology and philosophy that vied with Thomism throughout the late Middle Ages.
John Duns Scotus
John Duns Scotus opposed the rationalists’ contention that philosophy is self-sufficient and adequate to satisfy the human desire for knowledge. In fact, he claimed that a pure philosopher, such as Aristotle, could not truly understand the human condition because he was ignorant of the Fall of Man and his need for grace and redemption. Unenlightened by Christian revelation, Aristotle mistook humankind’s present fallen state, in which all knowledge comes through the senses, for its natural condition, in which the object of knowledge would be coextensive with all being, including the being of God. The limitation of Aristotle’s philosophy was apparent to Duns Scotus in the Aristotelian proof of the existence of God as the primary mover of the universe. More adequate than this physical proof, he contended, is his own very intricate metaphysical demonstration of the existence of God as the absolutely primary, unique, and infinite being. He incorporated the Anselmian argument into this demonstration. For Duns Scotus, the notion of infinite being, not that of primary mover or being itself, is humankind’s most perfect concept of God.
In opposition to the Greco-Arabic view of the government of the universe from above by necessary causes, Duns Scotus stressed the contingency of the universe and its total dependence on God’s infinite creative will. He adopted the traditional Franciscan voluntarism, elevating the will above the intellect in human beings.
Duns Scotus’s doctrine of universals justly earned him the title “Doctor Subtilis.” Universals, in his view, exist only as abstract concepts, but they are based on common natures, such as humanity, which exist, or can exist, in many individuals. Common natures are real, and they have a real unity of their own distinct from the unity of the individuals in which they exist. The individuality of each individual is due to an added positive reality that makes the common nature a specific individual—e.g., Socrates. Duns Scotus calls such a reality an “individual difference,” or “thisness” (haecceitas). It is an original development of the earlier medieval realism of universals.
William Of Ockham
In the late 14th century, Thomism and Scotism were called the “old way” (via antiqua) of philosophizing, in contrast to the “modern way” (via moderna) begun by philosophers such as William of Ockham. Ockham, no less than Duns Scotus, wanted to defend the Christian doctrine of the freedom and omnipotence of God and the contingency of creatures against the necessitarianism of Greco-Arabic philosophy. But for him the freedom of God is incompatible with the existence of divine ideas as positive models of creation. God does not use preconceived ideas when he creates, as Duns Scotus maintained, but he fashions the universe as he wishes. As a result, creatures have no natures, or essences, in common. There are no realities but individual things, and these have nothing in common. They are more or less like each other, however, and on this basis human beings can form universal concepts of them and talk about them in general terms.
The absolute freedom of God was often used by Ockham as a principle of philosophical and theological explanation. Because the order of nature has been freely created by God, it could have been different: fire, for example, could cool as it now heats. If God wishes, he can give us the sight, or “intuitive knowledge,” of a star without the reality of the star. The moral order could also have been different. God could have made hating him meritorious instead of loving him. It was typical of Ockham not to put too much trust in the power of human reason to reach the truth. For him, philosophy must often be content with probable arguments, as in establishing the existence of the Christian God. Faith alone gives certitude in this and in other vital matters. Another principle invoked by Ockham is that a plurality is not to be posited without necessity. This principle of economy of thought, later stated as “beings are not to be multiplied without necessity,” is called “Ockham’s razor.”
Ockhamism was censured by a papal commission at Avignon in 1326, and in 1474 it was forbidden to be taught at Paris. Nevertheless, it spread widely in the late Middle Ages and rivaled Thomism and Scotism in popularity. Other Scholastics in the 14th century shared Ockham’s basic principles and contributed with him to skepticism and probabilism in philosophy. John of Mirecourt (flourished 14th century) stressed the absolute power of God and the divine will to the point of making God the cause of human sin. Nicholas of Autrecourt (c. 1300–c. 1350) adopted a skeptical attitude regarding matters such as the ability of human beings to prove the existence of God and the reality of substance and causality. Rejecting Aristotelianism as inimical to the Christian faith, he advocated a return to the atomism of the ancient Greeks as a more adequate explanation of the universe.
Meister Eckehart
The trend away from Aristotelianism was accentuated by the German Dominican Meister Eckehart (c. 1260–c. 1327), who developed a speculative mysticism of both Christian and Neoplatonic inspiration. Eckehart depicted the ascent of the soul to God in Neoplatonic terms: by gradually purifying itself from the body, the soul transcends being and knowledge until it is absorbed in the One. The soul is then united with God at its highest point, or “citadel.” God himself transcends being and knowledge. Sometimes Eckehart describes God as the being of all things. This language, which was also used by Erigena and other Christian Neoplatonists, leaves him open to the charge of pantheism (the doctrine that the being of creatures is identical with that of God); but for Eckehart there is an infinite gulf between creatures and God. Eckehart meant that creatures have no existence of their own but are given existence by God, as the body is made to exist and is contained by the soul. Eckehart’s profound influence can be seen in the flowering of mysticism in the German Rhineland in the late Middle Ages.
Nicholas of Cusa
Nicholas of Cusa (1401–64) also preferred the Neoplatonists to the Aristotelians. To him the philosophy of Aristotle is an obstacle to the mind in its ascent to God because its primary rule is the principle of contradiction, which denies the compatibility of contradictories. But God is the “coincidence of opposites.” Because he is infinite, he embraces all things in perfect unity; he is at once the maximum and the minimum. Nicholas uses mathematical symbols to illustrate how, in infinity, contradictories coincide. If a circle is enlarged, the curve of its circumference becomes less; if a circle is infinite, its circumference is a straight line. As for human knowledge of the infinite God, one must be content with conjecture or approximation to the truth. The absolute truth escapes human beings; their proper attitude is “learned ignorance.”
For Nicholas, God alone is absolutely infinite. The universe reflects this divine perfection and is relatively infinite. It has no circumference, for it is limited by nothing outside of itself. Neither has it a centre; the Earth is neither at the centre of the universe nor is it completely at rest. Place and motion are not absolute but relative to the observer. This new, non-Aristotelian conception of the universe anticipated some of the features of modern theories.
Thus, at the end of the Middle Ages, some of the most creative minds were abandoning Aristotelianism and turning to newer ways of thought. The philosophy of Aristotle, in its various interpretations, continued to be taught in the universities, but it had lost its vitality and creativity. Christian philosophers were once again finding inspiration in Neoplatonism. The Platonism of the Renaissance was directly continuous with the Platonism of the Middle Ages.
Renaissance philosophy
The philosophy of a period arises as a response to social need, and the development of philosophy in the history of Western civilization since the Renaissance has, thus, reflected the process in which creative philosophers have responded to the unique challenges of each stage in the development of Western culture itself.
The career of philosophy—how it views its tasks and functions, how it defines itself, the special methods it invents for the achievement of philosophical knowledge, the literary forms it adopts and utilizes, its conception of the scope of its subject matter, and its changing criteria of meaning and truth—hinges on the mode of its successive responses to the challenges of the social structure within which it arises. Thus, Western philosophy in the Middle Ages was primarily a Christian philosophy, complementing the divine revelation, reflecting the feudal order in its cosmology, devoting itself in no small measure to the institutional tasks of the Roman Catholic Church. It was no accident that the major philosophical achievements of the 13th and 14th centuries were the work of churchmen who also happened to be professors of theology at the Universities of Oxford and Paris.
The Renaissance of the late 15th and 16th centuries presented a different set of problems and therefore suggested different lines of philosophical endeavour. What is called the European Renaissance followed the introduction of three novel mechanical inventions from the East: gunpowder, block printing from movable type, and the compass. The first was used to explode the massive fortifications of the feudal order and thus became an agent of the new spirit of nationalism that threatened the rule of churchmen—and, indeed, the universalist emphasis of the church itself—with a competing secular power. The second, printing, propagated knowledge widely, secularized learning, reduced the intellectual monopoly of an ecclesiastical elite, and restored the literary and philosophical classics of Greece and Rome. The third, the compass, increased the safety and scope of navigation, produced the voyages of discovery that opened up the Western Hemisphere, and symbolized a new spirit of physical adventure and a new scientific interest in the structure of the natural world.
Each of these inventions, with its wider cultural consequences, presented new intellectual problems and novel philosophical tasks within a changing political and social environment. As the power of a single religious authority was slowly eroded under the influence of the Protestant Reformation and as the prestige of the universal Latin language gave way to vernacular tongues, philosophers became less and less identified with their positions in the ecclesiastical hierarchy and more and more identified with their national origins. The works of Albertus Magnus, St. Thomas Aquinas, St. Bonaventure, and John Duns Scotus had been basically unrelated to the countries of their birth; but the philosophy of Niccolò Machiavelli (1469–1527) was directly related to Italian experience, and that of Francis Bacon (1561–1626) was English to the core, as was that of Thomas Hobbes (1588–1679) in the early modern period. Likewise, the thought of René Descartes (1596–1650) set the standard and tone of intellectual life in France for 200 years. (See below Modern philosophy.)
Knowledge in the contemporary world is conventionally divided between the natural sciences, the social sciences, and the humanities. In the Renaissance, however, fields of learning had not yet become so sharply departmentalized; in fact, each of these divisions arose in the comprehensive and broadly inclusive area of philosophy. As the Renaissance mounted its revolt against the reign of religion and therefore reacted against the church, against authority, against Scholasticism, and against Aristotle, there was a sudden blossoming of interest in problems centring on civil society, humankind, and nature. These three areas corresponded exactly to the three dominant strands of Renaissance philosophy: political philosophy, humanism, and the philosophy of nature.
Political philosophy
As secular authority replaced ecclesiastical authority and as the dominant interest of the age shifted from religion to politics, it was natural that the rivalries of the national states and their persistent crises of internal order should raise with renewed urgency philosophical problems, practically dormant since pre-Christian times, about the nature and the moral status of political power. This new preoccupation with national unity, internal security, state power, and international justice stimulated the growth of political philosophy in Italy, France, England, and Holland.
Machiavelli, sometime state secretary of the Florentine republic, explored techniques for the seizure and retention of power in ways that seemed to exalt “reasons of state” above morality. His The Prince and Discourses on the First Ten Books of Livy (both published posthumously) codified the actual practices of Renaissance diplomacy for the next 100 years. In fact, Machiavelli was motivated by patriotic hopes for the ultimate unification of Italy and by the conviction that the moral standards of contemporary Italians needed to be elevated by restoring the ancient Roman virtues. More than half a century later, the French political philosopher Jean Bodin (1530–96) insisted that the state must possess a single, unified, and absolute power; he thus developed in detail the doctrine of national sovereignty as the source of all legal legitimacy.
In England, Hobbes, who was to become tutor to the future king Charles II (1630–85), developed the fiction that, in the “state of nature” that preceded civilization, “every man’s hand [was] raised against every other” and human life was accordingly “solitary, poor, nasty, brutish, and short.” A social contract was thus agreed upon to convey all private rights to a single sovereign in return for general protection and the institution of a reign of law. Because law is simply “the command of the sovereign,” Hobbes at once turned justice into a by-product of power and denied any right of rebellion except when the sovereign becomes too weak to protect the commonwealth or to hold it together. (See below The materialism of Thomas Hobbes.)
In Holland, a prosperous and tolerant commercial republic in the 17th century, the issues of political philosophy took a different form. The Dutch East India Company commissioned a great jurist, Hugo Grotius (1583–1645), to write a defense of their trading rights and their free access to the seas, and the resulting two treatises, The Freedom of the Seas (1609) and On the Law of War and Peace (1625), were the first significant codifications of international law. Their philosophical originality lay, however, in the fact that, in defending the rights of a small, militarily weak nation against the powerful states of England, France, and Spain, Grotius was led to a preliminary investigation of the sources and validity of the concept of natural law—the notion that inherent in human reason and immutable even against the willfulness of sovereign states are imperative considerations of natural justice and moral responsibility, which must serve as a check against the arbitrary exercise of vast political power.
In general, the political philosophy of the Renaissance and the early modern period was dualistic: it was haunted, even confused, by the conflict between political necessity and general moral responsibility. Machiavelli, Bodin, and Hobbes asserted claims that justified the actions of Italian despotism and the absolutism of the Bourbon and Stuart dynasties. Yet Machiavelli was obsessed with the problem of human virtue, Bodin insisted that even the sovereign ought to obey the law of nature (that is, to govern in accordance with the dictates of natural justice), and Hobbes himself found in natural law the rational motivation that causes a person to seek security and peace. In the end, Renaissance and early modern political philosophy advocated the doctrines of Thrasymachus, who held that right is what is in the interests of the strong, but it could never finally escape a twinge of Socratic conscience.
The Renaissance was characterized by the revival of interest in mathematics, medicine, and Classical literature. The study of mathematics and medicine sparked the scientific revolution of the 16th and 17th centuries, while the study of Classical literature became the foundation of the philosophy of Renaissance humanism. Generally suspicious of science and indifferent to religion, humanism emphasized anew the centrality of human beings in the universe and their supreme value and importance. Characteristic of this emphasis was the Oration on the Dignity of Man (1486) by Giovanni Pico della Mirandola, an Italian Platonist philosopher and a leading member of the Platonic Academy of Florence, organized by the city’s ruler, Lorenzo de’ Medici (1449–92). But the new emphasis on personal responsibility and the possibility of self-creation as a work of art was in no small part a consequence of the rediscovery of a series of crucial Classical texts, which served to reverse the trends of medieval learning. Renaissance humanism was predicated upon the victory of rhetoric over dialectic and of Plato over Aristotle as the cramped format of Scholastic philosophical method gave way to a Platonic discursiveness.
Much of this transformation had been prepared by Italian scholarly initiative in the early 15th century. Lorenzo Valla (1407–57), an antiauthoritarian humanist, used the recently discovered manuscript of Institutio oratoria by Quintilian (35–c. 96) to create new forms of rhetoric and textual criticism. But even more important was the rebirth of an enthusiasm for the philosophy of Plato in Medici Florence and at the cultivated court of Urbino. Precisely to service this enthusiasm, Marsilio Ficino (1433–99), head of the Platonic Academy, translated the entire Platonic corpus into Latin by the end of the 15th century.
Except in the writings of Pico della Mirandola and of the Italian philosopher Giordano Bruno (1548–1600), the direct influence of Platonism on Renaissance metaphysics is difficult to trace. The Platonic account of the moral virtues, however, was admirably adapted to the requirements of Renaissance education, serving as a philosophical foundation of the Renaissance ideal of the courtier and gentleman. But Plato also represented the importance of mathematics and the Pythagorean attempt to discover the secrets of the heavens, the Earth, and the world of nature in terms of number and exact calculation. This aspect of Platonism influenced Renaissance science as well as philosophy. The scientists Nicolaus Copernicus (1473–1543), Johannes Kepler (1571–1630), and Galileo Galilei (1564–1642) owe a great deal to the general climate of Pythagorean confidence in the explanatory power of number.
Platonism also affected the literary forms in which Renaissance philosophy was written. Although very early medieval Platonists, such as St. Augustine and John Scotus Erigena, occasionally used the dialogue form, later Scholastics abandoned it in favour of the formal treatise, of which the great “summae” of Alexander of Hales (c. 1170–1245) and Aquinas were pristine examples. The Renaissance rediscovery of the Platonic dialogues suggested the literary charm of this conversational method to humanists, scientists, and political philosophers alike. Bruno put forth his central insights in a dialogue, Concerning the Cause, Principle, and One (1584); Galileo presented his novel mechanics in his Dialogue Concerning the Two Chief World Systems—Ptolemaic and Copernican (1632); and even Machiavelli’s The Art of War (1521) takes the form of a genteel conversation in a quiet Florentine garden.
Renaissance humanism was primarily a moral and a literary, rather than a narrowly philosophical, movement. It flowered in figures with broadly philosophical interests, such as Desiderius Erasmus (1469–1536), the erudite citizen of the world, and Sir Thomas More (1477–1535), the learned but unfortunate chancellor of Henry VIII, as well as, in the next generation, the great French essayist Michel de Montaigne (1532–92). But the recovery of the Greek and Latin classics, which was the work of humanism, profoundly affected the entire field of Renaissance and early modern philosophy and science through the ancient schools of philosophy to which it once more directed attention. In addition to Platonism, the most notable of these schools were atomism, Skepticism, and Stoicism. The discovery of Lucretius’s De rerum natura influenced Galileo, Bruno, and later Pierre Gassendi (1592–1655), a modern Epicurean, through the insights into nature reflected in this work. The recovery of Sextus Empiricus’s Outlines of Pyrrhonism, reprinted in 1562, produced a skeptical crisis in French philosophy that dominated the period from Montaigne to Descartes. And the Stoicism of Seneca and Epictetus became almost the official ethics of the Renaissance, figuring prominently in the Essays (1580–88) of Montaigne, in the letters that Descartes wrote to Princess Elizabeth of Bohemia (1618–79) and to Queen Christina of Sweden (1626–89), and in the later sections of the Ethics (1675) of Benedict de Spinoza (1632–77).
Philosophy of nature
Philosophy in the modern world is a self-conscious discipline. It has managed to define itself narrowly, distinguishing itself on the one hand from religion and on the other from exact science. But this narrowing of focus came about very late in its history—certainly not before the 18th century. The earliest philosophers of ancient Greece were theorists of the physical world; Pythagoras and Plato were at once philosophers and mathematicians, and in Aristotle there is no clear distinction between philosophy and natural science. The Renaissance and early modern period continued this breadth of conception characteristic of the Greeks. Galileo and Descartes were at once mathematicians, physicists, and philosophers; and physics retained the name natural philosophy at least until the death of Sir Isaac Newton (1642–1727).
Had the thinkers of the Renaissance been painstaking in the matter of definition (which they were not), they might have defined philosophy, on the basis of its actual practice, as “the rational, methodical, and systematic consideration of humankind, civil society, and the natural world.” Philosophy’s areas of interest would thus not have been in doubt, though the issue of what constitutes “rational, methodical, and systematic consideration” would have been extremely controversial. Because knowledge advances through the discovery and advocacy of new philosophical methods and because these diverse methods depend for their validity on prevailing philosophical criteria of truth, meaning, and importance, the crucial philosophical quarrels of the 16th and 17th centuries were at bottom quarrels about method. It is this issue, rather than any disagreement over subject matter or areas of interest, that divided the greatest Renaissance philosophers.
The great new fact that confronted the Renaissance was the immediacy, the immensity, and the uniformity of the natural world. But what was of primary importance was the new perspective through which this fact was interpreted. To the Schoolmen of the Middle Ages, the universe was hierarchical, organic, and God-ordained. To the philosophers of the Renaissance, it was pluralistic, machinelike, and mathematically ordered. In the Middle Ages, scholars thought in terms of purposes, goals, and divine intentions; in the Renaissance, they thought in terms of forces, mechanical agencies, and physical causes. All of this had become clear by the end of the 15th century. Within the early pages of the Notebooks of Leonardo da Vinci (1452–1519), the great Florentine artist and polymath, occur the following three propositions:
1. Since experience has been the mistress of whoever has written well, I take her as my mistress, and to her on all points make my appeal.
2. Instrumental or mechanical science is the noblest and above all others the most useful, seeing that by means of it all animated bodies which have movement perform all their actions.
3. There is no certainty where one can neither apply any of the mathematical sciences, nor any of those which are based upon the mathematical sciences.
Here are enunciated respectively (1) the principle of empiricism, (2) the primacy of mechanistic science, and (3) faith in mathematical explanation. It is upon these three doctrines, as upon a rock, that Renaissance and early modern science and philosophy were built. From each of Leonardo’s theses descended one of the great streams of Renaissance and early modern philosophy: from the empirical principle the work of Bacon, from mechanism the work of Hobbes, and from mathematical explanation the work of Descartes.
Any adequate philosophical treatment of scientific method recognizes that the explanations offered by science are both empirical and mathematical. In Leonardo’s thinking, as in scientific procedure generally, there need be no conflict between these two ideals; yet they do represent two opposite poles, each capable of excluding the other. The peculiar accidents of Renaissance scientific achievement did mistakenly suggest their incompatibility, for the revival of medical studies on the one hand and the blooming of mathematical physics on the other emphasized opposite virtues in scientific methodology. This polarity was represented by the figures of Andreas Vesalius (1514–64) and Galileo.
Vesalius, a Flemish physician, astounded all of Europe with the unbelievable precision of his anatomical dissections and drawings. Having invented new tools for this precise purpose, he successively laid bare the vascular, neural, and muscular systems of the human body. This procedure seemed to demonstrate the virtues of empirical method, of experimentation, and of inductive generalization on the basis of precise and disciplined observation.
Only slightly later, Galileo, following in the tradition already established by Copernicus and Kepler, attempted to do for terrestrial and sidereal movement what Vesalius had managed for the structure of the human body—creating his physical dynamics, however, on the basis of hypotheses derived from mathematics. In Galileo’s work, all of the most original scientific impulses of the Renaissance were united: the interest in Hellenistic mathematics, the experimental use of new instruments such as the telescope, and the underlying faith that the search for certainty in science is reasonable because the motions of all physical bodies are comprehensible in mathematical terms. Galileo’s work also deals with some of the recurrent themes of 16th- and 17th-century philosophy: atomism (which describes the changes of gross physical bodies in terms of the motions of their parts), the reduction of qualitative differences to quantitative differences, and the resultant important distinction between “primary” and “secondary” qualities. The former qualities—including shape, extension, and specific gravity—were considered to be part of nature and therefore real. The latter—such as colour, odour, taste, and relative position—were taken to be simply the effect of the motions of physical bodies on perceiving minds and therefore ephemeral, subjective, and essentially irrelevant to the nature of physical reality.

Modern philosophy

The rise of empiricism and rationalism
The scientific contrast between Vesalius’s rigorous observational techniques and Galileo’s reliance on mathematics was similar to the philosophical contrast between Bacon’s experimental method and Descartes’s emphasis on a priori reasoning. Indeed, these differences can be conceived in more abstract terms as the contrast between empiricism and rationalism. This theme dominated the philosophical controversies of the 17th and 18th centuries and was hardly resolved before the advent of Immanuel Kant.
The Empiricism Of Francis Bacon
Sir Francis Bacon was the outstanding apostle of Renaissance empiricism. Less an original metaphysician or cosmologist than the advocate of a vast new program for the advancement of learning and the reformation of scientific method, Bacon conceived of philosophy as a new technique of reasoning that would reestablish natural science on a firm foundation. In the Advancement of Learning (1605), he charted the map of knowledge: history, which depends on the human faculty of memory, poetry, which depends on imagination, and philosophy, which depends on reason. To reason, however, Bacon assigned a completely experiential function. Fifteen years later, in his Novum Organum, he made this clear: Because, he said, “we have as yet no natural philosophy which is pure,…the true business of philosophy must be…to apply the understanding…to a fresh examination of particulars.” A technique for “the fresh examination of particulars” thus constituted his chief contribution to philosophy.
Bacon’s hope for a new birth of science depended not only on vastly more numerous and varied experiments but primarily on “an entirely different method, order, and process for advancing experience.” This method consisted of the construction of what he called “tables of discovery.” He distinguished three kinds: tables of presence, of absence, and of degree (i.e., in the case of any two properties, such as heat and friction, instances in which they appear together, instances in which one appears without the other, and instances in which their amounts vary proportionately). The ultimate purpose of these tables was to order facts in such a way that the true causes of phenomena (the subject of physics) and the true “forms” of things (the subject of metaphysics—the study of the nature of being) could be inductively established.
Bacon’s empiricism was not raw or unsophisticated. His concept of fact and his belief in the primacy of observation led him to formulate laws and generalizations. Also, his conception of forms was quite un-Platonic: a form for him was not an essence but a permanent geometric or mechanical structure. His enduring place in the history of philosophy lies, however, in his single-minded advocacy of experience as the only source of valid knowledge and in his profound enthusiasm for the perfection of natural science. It is in this sense that “the Baconian spirit” was a source of inspiration for generations of later philosophers and scientists.
The Materialism of Thomas Hobbes
Thomas Hobbes was acquainted with both Bacon and Galileo. With the first he shared a strong concern for philosophical method, with the second an overwhelming interest in matter in motion. His philosophical efforts, however, were more inclusive and more complete than those of his contemporaries. He was a comprehensive thinker within the scope of an exceedingly narrow set of presuppositions, and he produced one of the most systematic philosophies of the early modern period—an almost completely consistent description of humankind, civil society, and nature according to the tenets of mechanistic materialism.
Hobbes’s account of what philosophy is and ought to be clearly distinguished between content and method. As method, philosophy is simply reasoning or calculating by the use of words as to the causes or effects of phenomena. When a person reasons from causes to effects, he reasons synthetically; when he reasons from effects to causes, he reasons analytically. (Hobbes’s strong inclination toward deduction and geometric proofs favoured arguments of the former type.) His dogmatic metaphysical assumption was that physical reality consists entirely of matter in motion. The real world is a corporeal universe in constant movement, and phenomena, or events, the causes and effects of which it is the business of philosophy to lay bare, consist of either the action of physical bodies on each other or the quaint effects of physical bodies upon minds. From this assumption follows Hobbes’s classification of the fields that form the content of philosophy: (1) physics, (2) moral philosophy, and (3) civil philosophy. Physics is the science of the motions and actions of physical bodies conceived in terms of cause and effect. Moral philosophy (or, more accurately, psychology) is the detailed study of “the passions and perturbations of the mind”—that is, how minds are “moved” by desire, aversion, appetite, fear, anger, and envy. And civil philosophy deals with the concerted actions of people in a commonwealth—how, in detail, the wayward wills of human beings can be constrained by power (i.e., force) to prevent civil disorder and maintain peace.
Hobbes’s philosophy was a bold restatement of Greek atomistic materialism, with applications to the realities of early modern politics that would have seemed strange to its ancient authors. But there are also elements in it that make it characteristically English. Hobbes’s account of language led him to adopt nominalism and to deny the reality of universals. Bacon’s general emphasis on experience also had its analogue in Hobbes’s theory that all knowledge arises from sense experiences, all of which are caused by the actions of physical bodies on the sense organs. Empiricism has been a basic and recurrent feature of British intellectual life, and its nominalist and sensationalist roots were already clearly evident in both Bacon and Hobbes.
The Rationalism of Descartes
The dominant philosophy of the last half of the 17th century was that of René Descartes. A crucial figure in the history of philosophy, Descartes combined (however unconsciously or even unwillingly) the influences of the past into a synthesis that was striking in its originality and yet congenial to the scientific temper of the age. In the minds of all later historians, he counts as the progenitor of the modern spirit of philosophy.
From the past there seeped into the Cartesian synthesis doctrines about God from Anselm and Aquinas, a theory of the will from Augustine, a deep sympathy with the Stoicism of the Romans, and a skeptical method taken indirectly from Pyrrho and Sextus Empiricus. But Descartes was also a great mathematician—he invented analytic geometry—and the author of many important physical and anatomical experiments. He knew and profoundly respected the work of Galileo; indeed, he withdrew from publication his own cosmological treatise, The World, after Galileo’s condemnation by the Inquisition in 1633.
Each of the maxims of Leonardo, which constitute the Renaissance worldview, found its place in Descartes: empiricism in the physiological researches described in the Discourse on Method (1637), a mechanistic interpretation of the physical world and of human action in the Principles of Philosophy (1644) and The Passions of the Soul (1649), and a mathematical bias that dominates the theory of method in Rules for the Direction of the Mind (1701) and the metaphysics of the Meditations on the First Philosophy (1642). But it is the mathematical theme that clearly predominates in Descartes’s philosophy.
Bacon and Descartes, the founders of modern empiricism and rationalism, respectively, both subscribed to two pervasive tenets of the Renaissance: an enormous enthusiasm for physical science and the belief that knowledge means power—that the ultimate purpose of theoretical science is to serve the practical needs of human beings.
In his Principles, Descartes defined philosophy as “the study of wisdom” or “the perfect knowledge of all one can know.” Its chief utility is “for the conduct of life” (morals), “the conservation of health” (medicine), and “the invention of all the arts” (mechanics). He expressed the relation of philosophy to practical endeavours in the famous metaphor of the “tree”: the roots are metaphysics, the trunk is physics, and the branches are morals, medicine, and mechanics. The metaphor is revealing, for it indicates that for Descartes—as for Bacon and Galileo—the most important part of the tree was the trunk. In other words, Descartes busied himself with metaphysics only in order to provide a firm foundation for physics. Thus, the Discourse on Method, which provides a synoptic view of the Cartesian philosophy, shows it to be not a metaphysics founded upon physics (as was the case with Aristotle) but rather a physics founded upon metaphysics.
Descartes’s mathematical bias was reflected in his determination to ground natural science not in sensation and probability (as did Bacon) but in premises that could be known with absolute certainty. Thus his metaphysics in essence consisted of three principles:
To employ the procedure of complete and systematic doubt to eliminate every belief that does not pass the test of indubitability (skepticism).
To accept no idea as certain that is not clear, distinct, and free of contradiction (mathematicism).
To found all knowledge upon the bedrock certainty of self-consciousness, so that “I think, therefore I am” becomes the only innate idea unshakable by doubt (subjectivism).
From the indubitability of the self, Descartes inferred the existence of a perfect God; and, from the fact that a perfect being is incapable of falsification or deception, he concluded that the ideas about the physical world that God has implanted in human beings must be true. The achievement of certainty about the natural world was thus guaranteed by the perfection of God and by the “clear and distinct” ideas that are his gift.
Cartesian metaphysics is the fountainhead of rationalism in modern philosophy, for it suggests that the mathematical criteria of clarity, distinctness, and logical consistency are the ultimate test of meaningfulness and truth. This stance is profoundly antiempirical. Bacon, who remarked that “reasoners resemble spiders who make cobwebs out of their own substance,” might well have said the same of Descartes, for the Cartesian self is just such a substance. Yet for Descartes the understanding is vastly superior to the senses, and only reason can ultimately decide what constitutes truth in science.
Cartesianism dominated the intellectual life of continental Europe until the end of the 17th century. It was a fashionable philosophy, appealing to learned gentlemen and highborn ladies alike, and it was one of the few philosophical alternatives to the Scholasticism still being taught in the universities. Precisely for this reason it constituted a serious threat to established religious authority. In 1663 the Roman Catholic Church placed Descartes’s works on the Index Librorum Prohibitorum (“Index of Forbidden Books”), and the University of Oxford forbade the teaching of his doctrines. Only in the liberal Dutch universities, such as those of Groningen and Utrecht, did Cartesianism make serious headway.
Certain features of Cartesian philosophy made it an important starting point for subsequent philosophical speculation. As a kind of meeting point for medieval and modern worldviews, it accepted the doctrines of Renaissance science while attempting to ground them metaphysically in medieval notions of God and the human mind. Thus, a certain dualism between God the Creator and the mechanistic world of his creation, between mind as a spiritual principle and matter as mere spatial extension, was inherent in the Cartesian position. An entire generation of Cartesians—among them Arnold Geulincx, Nicolas Malebranche, and Pierre Bayle—wrestled with the resulting problem of how interaction between two such radically different entities is possible.
The Rationalism of Spinoza and Leibniz
The tradition of Continental rationalism was carried on by two philosophers of genius: the Dutch Jewish philosopher Benedict de Spinoza (1632–77) and his younger contemporary Gottfried Wilhelm Leibniz (1646–1716), a Leipzig scholar and polymath. Whereas Bacon’s philosophy had been a search for method in science and Descartes’s basic aim had been the achievement of scientific certainty, Spinoza’s speculative system was one of the most comprehensive of the early modern period. In certain respects Spinoza had much in common with Hobbes: a mechanistic worldview and even a political philosophy that sought political stability in centralized power. Yet Spinoza introduced a conception of philosophizing that was new to the Renaissance; philosophy became a personal and moral quest for wisdom and the achievement of human perfection.
Spinoza’s magnum opus, the Ethics, borrowed much from Descartes: the goal of a rational understanding of principles, the terminology of “substance” and “clear and distinct ideas,” and the expression of philosophical knowledge in a complete deductive system using the geometric model of the Elements of Euclid (flourished c. 300 bc). Spinoza conceived of the universe pantheistically as a single infinite substance, which he called “God,” with the dual attributes (or aspects) of thought and extension (see pantheism). Extension is differentiated into plural “modes,” or particular things, and the world as a whole possesses the properties of a timeless logical system—a complex of completely determined causes and effects. For Spinoza, the wisdom that philosophy seeks is ultimately achieved when one perceives the universe in its wholeness through the “intellectual love of God,” which merges the finite individual with eternal unity and provides the mind with the pure joy that is the final achievement of its search.
Whereas the basic elements of the Spinozistic worldview are given in the Ethics, Leibniz’s philosophy must be pieced together from numerous brief expositions, which seem to be mere philosophical interludes in an otherwise busy life. But the philosophical form is deceptive. Leibniz was a mathematician (he and Sir Isaac Newton independently invented the infinitesimal calculus), a jurist (he codified the laws of Mainz), a diplomat, a historian to royalty, and a court librarian in a princely house. Yet he was also one of the most original philosophers of the early modern period. His chief contributions were in the fields of logic, in which he was a truly brilliant innovator, and metaphysics, in which he provided a rationalist alternative to the philosophies of Descartes and Spinoza. Leibniz conceived of logic as a mathematical calculus. He was the first to distinguish “truths of reason” from “truths of fact” and to contrast the necessary propositions of logic and mathematics, which hold in all “possible worlds,” with the contingent propositions of science, which hold only in some possible worlds (including the actual world). He saw clearly that, as the first kind of proposition is governed by the principle of contradiction (a proposition and its negation cannot both be true), the second is governed by the principle of sufficient reason (nothing exists or is the case without a sufficient reason).
In metaphysics, Leibniz’s pluralism contrasted with Descartes’s dualism and Spinoza’s monism (see pluralism and monism). Leibniz posited the existence of an infinite number of spiritual substances, which he called “monads,” each different, each a percipient of the universe around it, and each mirroring that universe from its own point of view. However, the differences between Leibniz’s philosophy and that of Descartes and Spinoza are less significant than their similarities, in particular their extreme rationalism. In the Principes de la nature et de la grâce fondés en raison (1714; “Principles of Nature and of Grace Founded in Reason”), Leibniz stated a maxim that could fairly represent the entire school:
True reasoning depends upon necessary or eternal truths, such as those of logic, numbers, geometry, which establish an indubitable connection of ideas and unfailing consequences.
Literary forms and sociological conditions
The literary forms in which philosophical exposition was couched in the early modern period ranged from the scientific aphorisms of Bacon and the autobiographical meditations of Descartes to the systematic prose of Hobbes and the episodic propositional format of Leibniz. Two basic tendencies, however, can be discerned:
The early Renaissance commitment to the dialogue form (already noted), inspired by the rediscovery of the Platonic dialogues.
The later prevalence of the systematically ordered treatise, undoubtedly influenced by the enormous prestige of deductive mathematics.
The concept of serial order stressed by geometry, in which the reasoner passes deductively from the universal (axioms) to the particular (theorems), influenced, in turn, the style of Hobbes, Descartes, and Spinoza. The organization of Hobbes’s Leviathan and Descartes’s Principles reflects this tendency, while Spinoza’s Ethics utilizes the Euclidean method so formalistically as almost to constitute an impenetrable barrier to the basic lucidity of his thought.
Medieval philosophy was characteristically associated with the medieval university. It is a singular fact, therefore, that from the birth of Bacon in 1561 to the death of the Scottish philosopher David Hume in 1776—i.e., for more than 200 years—not one first-rate philosophical mind in Europe was permanently associated with a university.
As the age of the saint passed into that of the gentleman, the changing social, political, and economic conditions were naturally reflected in the titles, social status, and economic situation of philosophers. Bacon was a lawyer, judge, and attendant upon the royal court; Hobbes was the tutor and companion of young noblemen;
Descartes, the son of a noble family, traveled and studied at leisure, eventually retiring to Holland on an inherited income; and Leibniz, courtier, diplomat, and scholar, was a privy councillor and baron of the Holy Roman Empire. Some philosophers also associated with the great monarchs and administrators of the age: Descartes gave philosophical instruction to Queen Christina of Sweden, Leibniz was an intimate of the electress Sophia Charlotte of Prussia (1668–1705), and Spinoza enjoyed the personal friendship of the Dutch politician Johan de Witt (1625–72). Thus, in the early modern period, philosophers often belonged to the lesser nobility or were closely associated with the higher nobility, to whom—like poets—many of them dedicated their works.
Thus philosophy in the 16th and 17th centuries was clearly the preoccupation of a widely scattered elite. This meant that, despite the existence of printing, much philosophical communication took place within a small and informal circle. Treatises were circulated in manuscript, comments and objections were solicited, and a vast polemical correspondence was built up. Prior to its publication, Descartes prudently sent his Meditations to the theologians of the Sorbonne for comment; after its publication, his friend Marin Mersenne (1588–1648) sent it to Hobbes, Antoine Arnauld (1612–94), and Pierre Gassendi, among others, who returned formal objections to which Descartes in turn replied. The rich philosophical correspondence of the 17th century is exemplified by the letters that passed between Descartes and the scientist Christiaan Huygens (1629–95), between Leibniz and Arnauld, and between Leibniz and Samuel Clarke (1675–1729), which were published in 1717.
Throughout the early modern period, creative philosophy was sharply separated from formal centres of learning. Hobbes expressed extreme contempt for the Aristotelianism of Oxford; Descartes, despite his prudence, scorned the medievalists of the Sorbonne; and Spinoza refused the offer of a professorship of philosophy at Heidelberg with polite aversion. It was to be another 100 years before philosophy returned to the universities.
The Enlightenment
Although they both lived and worked in the late 17th century, Sir Isaac Newton and John Locke (1632–1704) were the true fathers of the Enlightenment. Newton was the last of the scientific geniuses of the age, and his great Philosophiae Naturalis Principia Mathematica (1687; Mathematical Principles of Natural Philosophy) was the culmination of the movement that had begun with Copernicus and Galileo—the first scientific synthesis based on the application of mathematics to nature in every detail. The basic idea of the authority and autonomy of reason, which dominated all philosophizing in the 18th century, was, at bottom, the consequence of Newton’s work.
Copernicus, Kepler, Bacon, Galileo, and Descartes—scientists and methodologists of science—performed like people urgently attempting to persuade nature to reveal its secrets. Newton’s comprehensive mechanistic system made it seem as if at last nature had done so. It is impossible to exaggerate the enormous enthusiasm that this assumption kindled in all of the major thinkers of the late 17th and 18th centuries, from Locke to Kant. The new enthusiasm for reason that they all instinctively shared was based not upon the mere advocacy of philosophers such as Descartes and Leibniz but upon their conviction that, in the spectacular achievement of Newton, reason had succeeded in conquering the natural world.
Classical British Empiricism
Two major philosophical problems remained: to provide an account of the origins of reason and to shift its application from the physical universe to human nature. Locke’s Essay Concerning Human Understanding (1690) was devoted to the first, and Hume’s Treatise of Human Nature (1739–40), “being an attempt to apply the method of experimental reasoning to moral subjects,” was devoted to the second.
These two basic tasks represented a new direction for philosophy since the late Renaissance. The Renaissance preoccupation with the natural world had constituted a certain “realistic” bias. Hobbes and Spinoza had each produced a metaphysics. They had been interested in the real constitution of the physical world. Moreover, the Renaissance enthusiasm for mathematics had resulted in a profound interest in rational principles, necessary propositions, and innate ideas. As attention was turned from the realities of nature to the structure of the mind that knows it so successfully, philosophers of the Enlightenment focused on the sensory and experiential components of knowledge rather than on the merely mathematical. Thus, whereas the philosophy of the late Renaissance had been metaphysical and rationalistic, that of the Enlightenment was epistemological and empiricist. The school of British empiricism—John Locke, George Berkeley (1685–1753), and David Hume—dominated the perspective of Enlightenment philosophy until the time of Kant.
Reason in Locke and Berkeley
Locke’s An Essay Concerning Human Understanding marked a decisively new direction for modern philosophizing because it proposed what amounts to a new criterion of truth. Locke’s aim in his essay—“to inquire into the origin, certainty, and extent of human knowledge”—involved three tasks:
To discover the origin of human ideas.
To determine their certainty and evidential value.
To examine the claims of all knowledge that is less than certain.
What was crucial for Locke, however, was that the second task is dependent upon the first. Following the general Renaissance custom, Locke defined an idea as a mental entity: “whatever is the object of the understanding when a man thinks.” But whereas for Descartes and the entire rationalist school the certainty of ideas had been a function of their self-evidence—i.e., of their clarity and distinctness—for Locke their validity depended expressly on the mode and manner of their origin. Thus, an intrinsic criterion of truth and validity was replaced with a genetic one.
Locke’s exhaustive survey of mental contents is useful, if elaborate. Although he distinguished between ideas of sensation and ideas of reflection, the thrust of his efforts and those of his empiricist followers was to reduce the latter to the former, to minimize the originative power of the mind in favour of its passive receptivity to the sensory impressions received from without. Locke’s classification of ideas into “simple” and “complex” was an attempt to distinguish mental contents that are derived directly from one or more of the senses (such as blueness or solidity, which come from a single sense such as sight or touch, and figure, space, extension, rest, and motion, which are the product of several senses combined) from complicated and compounded ideas of universals (such as triangle and gratitude), substances, and relations (such as identity, diversity, and cause and effect).
Locke’s Essay was a dogged attempt to produce the total world of human conceptual experience from a set of elementary sensory building blocks, moving always from sensation toward thought and from the simple to the complex. The basic outcome of his epistemology was therefore:
That the ultimate source of human ideas is sense experience.
That all mental operations are a combining and compounding of simple sensory materials into complex conceptual entities.
Locke’s theory of knowledge was based upon a kind of sensory atomism, in which the mind is an agent of discovery rather than of creation, and ideas are “like” the objects they represent, which in turn are the sources of the sensations the mind receives. Locke’s theory also made the important distinction between “primary qualities” (such as solidity, figure, extension, motion, and rest), which are real properties of physical objects, and “secondary qualities” (such as colour, taste, and smell), which are merely the effects of such real properties on the mind.
It was precisely this dualism of primary and secondary qualities that Locke’s successor, George Berkeley, sought to overcome. Although Berkeley was a bishop in the Anglican church who professed a desire to combat atheistic materialism, his importance for the theory of knowledge lies rather in the way in which he demonstrated that, in the end, primary qualities are reducible to secondary qualities. His empiricism led to a denial of abstract ideas because he believed that general notions are simply fictions of the mind. Science, he argued, can easily dispense with the concept of matter: nature is simply that which human beings perceive through their sense faculties. This means that sense experiences themselves can be considered “objects for the mind.” A physical object, therefore, is simply a recurrent group of sense qualities. With this important reduction of substance to quality, Berkeley became the father of the epistemological position known as phenomenalism, which has remained an important influence in British philosophy to the present day.
Basic science of human nature in Hume
The third, and in many ways the most important, of the British empiricists was the skeptic David Hume. Hume’s philosophical intention was to reap, humanistically, the harvest sowed by Newtonian physics, to apply the method of natural science to human nature. The paradoxical result of this admirable goal, however, was a skeptical crisis even more devastating than that of the early French Renaissance.
Hume followed Locke and Berkeley in approaching the problem of knowledge from a psychological perspective. He too found the origin of knowledge in sense experience. But whereas Locke had found a certain trustworthy order in the compounding power of the mind, and Berkeley had found mentality itself expressive of a certain spiritual power, Hume’s relentless analysis discovered as much contingency in mind as in the external world. All uniformity in perceptual experience, he held, comes from “an associating quality of the mind.” The “association of ideas” is a fact, but the relations of resemblance, contiguity, and cause and effect that it produces have no intrinsic validity because they are merely the product of “mental habit.” Thus, the causal principle upon which all knowledge rests represents no necessary connections between things but is simply the result of their constant conjunction in human minds. Moreover, the mind itself, far from being an independent power, is simply “a bundle of perceptions” without unity or cohesive quality. Hume’s denial of a necessary order of nature on the one hand and of a substantial or unified self on the other precipitated a philosophical crisis from which Enlightenment philosophy was not to be rescued until the work of Kant.
Nonepistemological Movements In The Enlightenment
Although the school of British empiricism represented the mainstream of Enlightenment philosophy until the time of Kant, it was by no means the only type of philosophy that the 18th century produced. The Enlightenment, which was based upon a few great fundamental ideas—such as the dedication to reason, the belief in intellectual progress, the confidence in nature as a source of inspiration and value, and the search for tolerance and freedom in political and social institutions—generated many crosscurrents of intellectual and philosophical expression.
Materialism and scientific discovery
The profound influence of Locke spread to France, where it not only resulted in the skeptical empiricism of Voltaire (1694–1778) but also united with mechanistic aspects of Cartesianism to produce an entire school of sensationalistic materialism. Representative works included Man a Machine (1747) by Julien Offroy de La Mettrie (1709–51), Treatise on the Sensations (1754) by Étienne Bonnot de Condillac (1715–80), and The System of Nature (1770) by Paul-Henri Dietrich, baron d’Holbach (1723–89). This position even found its way into many of the articles of the great French Encyclopédie, edited by Denis Diderot (1713–84) and Jean d’Alembert (1717–83), which was almost a complete compendium of the scientific and humanistic accomplishments of the 18th century.
Although the terms Middle Ages and Renaissance were not invented until well after the historical periods they designate, scholars of the 18th century called their age “the Enlightenment” with self-conscious enthusiasm and pride. It was an age of optimism and expectations of new beginnings. Great strides were made in chemistry and biological science. Jean-Baptiste de Monet, chevalier de Lamarck (1744–1829), Georges, Baron Cuvier (1769–1832), and Georges-Louis Leclerc, comte de Buffon (1707–88), introduced a new system of animal classification. In the eight years between 1766 and 1774, three chemical elements—hydrogen, nitrogen, and oxygen—were discovered. Foundations were being laid in psychology and the social sciences and in ethics and aesthetics. The work of Anne-Robert-Jacques Turgot, baron de L’Aulne (1727–81), and Montesquieu (1689–1755) in France, Giambattista Vico (1668–1744) in Italy, and Adam Smith (1723–90) in Scotland marked the beginning of economics, politics, history, sociology, and jurisprudence as sciences. Hume, the utilitarian philosopher Jeremy Bentham (1748–1832), and the British “moral sense” theorists were turning ethics into a specialized field of philosophical inquiry. And Anthony Ashley, 3rd earl of Shaftesbury (1671–1713), Edmund Burke (1729–97), Johann Gottsched (1700–66), and Alexander Baumgarten (1714–62) were laying the foundations for a systematic aesthetics.
Social and political philosophy
Apart from epistemology, the most significant philosophical contributions of the Enlightenment were made in the fields of social and political philosophy. The Two Treatises of Civil Government (1690) by Locke and The Social Contract (1762) by Jean-Jacques Rousseau (1712–78) proposed justifications of political association grounded in the newer political requirements of the age. The Renaissance political philosophies of Machiavelli, Bodin, and Hobbes had presupposed or defended the absolute power of kings and rulers. But the Enlightenment theories of Locke and Rousseau championed the freedom and equality of citizens. It was a natural historical transformation. The 16th and 17th centuries were the age of absolutism; the chief problem of politics was that of maintaining internal order, and political theory was conducted in the language of national sovereignty. But the 18th century was the age of the democratic revolutions; the chief political problem was that of securing freedom and revolting against injustice, and political theory was expressed in the idiom of natural and inalienable rights.
Locke’s political philosophy explicitly denied the divine right of kings and the absolute power of the sovereign. Instead, he insisted on a natural and universal right to freedom and equality. The state of nature in which human beings originally lived was not, as Hobbes imagined, intolerable, though it did have certain inconveniences. Therefore, people banded together to form society—as Aristotle taught, “not simply to live, but to live well.” Political power, Locke argued, can never be exercised apart from its ultimate purpose, which is the common good, for the political contract is undertaken in order to preserve life, liberty, and property.
Locke thus stated one of the fundamental principles of political liberalism: that there can be no subjection to power without consent—though once political society has been founded, citizens are obligated to accept the decisions of a majority of their number. Such decisions are made on behalf of the majority by the legislature, though the ultimate power of choosing the legislature rests with the people; and even the powers of the legislature are not absolute, because the law of nature remains as a permanent standard and as a principle of protection against arbitrary authority.
Rousseau’s more radical political doctrines were built upon Lockean foundations. For him, too, the convention of the social contract formed the basis of all legitimate political authority, though his conception of citizenship was much more organic and much less individualistic than Locke’s. The surrender of natural liberty for civil liberty means that all individual rights (among them property rights) become subordinate to the general will. For Rousseau the state is a moral person whose life is the union of its members, whose laws are acts of the general will, and whose end is the liberty and equality of its citizens. It follows that when any government usurps the power of the people, the social contract is broken; and not only are the citizens no longer compelled to obey, but they also have an obligation to rebel. Rousseau’s defiant collectivism was clearly a revolt against Locke’s systematic individualism; for Rousseau the fundamental category was not “natural person” but “citizen.” Nevertheless, however much they differed, in these two social theorists of the Enlightenment is to be found the germ of all modern liberalism: its faith in representative democracy, in civil liberties, and in the basic dignity of human beings.
Professionalization of philosophy
In his Éléments de philosophie (1759; “Elements of Philosophy”), d’Alembert wrote:
Our century is the century of philosophy par excellence. If one considers without bias the present state of our knowledge, one cannot deny that philosophy among us has shown progress.
D’Alembert was calling attention to the self-examination for which the 18th century is famous, and he was undoubtedly referring to the activities of mathematicians (like himself), jurists, economists, and amateur moralists rather than to those of narrow philosophical specialists. But the 18th century was clearly the “century of philosophy par excellence” in a more technical sense also, for it was the period in which philosophizing first began to pass from the hands of gentlemen and amateurs into those of true professionals. The chief sign of this shift was the return of reputable philosophy to the universities.
This transformation first occurred in Germany and is mainly associated with the University of Halle (founded 1694). During the time of the generation between Leibniz and Kant, the philosophical climate changed profoundly. The best representative of this change was Christian Wolff (1679–1754), who taught philosophy at Halle. Kant called Wolff “the real originator of the spirit of thoroughness in Germany,” and Wolff was indeed a pioneer in techniques that transformed philosophy into a professional discipline: the self-conscious adoption of a systematic approach and the creation of a specialized philosophical vocabulary. Wolff carefully distinguished the various fields of philosophy, wrote textbooks in each of them, which were used in the German universities for many years, and created many of the specialized philosophical terms that have survived to the present day.
The German Enlightenment was the first modern period to produce specialists in philosophy. In England philosophizing in the universities did not become serious until well after the time of Hume, but already philosophical fields had been sufficiently distinguished to be represented by distinct professorships. The titles professor of mental philosophy, professor of moral philosophy, and professor of metaphysical philosophy, as they arose at Oxford and Cambridge, were the product of the late 18th and early 19th centuries.
Two additional features of the German Enlightenment are relevant: (1) the founding of the first professional journals and (2) the increasing concern of philosophy with its own history. The learned journal, like the scientific society, was an innovation of the 17th century. But what had begun as a general intellectual endeavour became in 18th-century Germany a specifically philosophical enterprise. Journals were published in great numbers: e.g., Acta Philosophorum (Halle, 1715–26), Der philosophische Büchersaal (Leipzig, 1741–44; “The Philosophical Book Room”), and the short-lived Neues philosophisches Magazin (Leipzig, 1789–91), devoted exclusively to the philosophy of Kant.
More interesting still is the publication of voluminous German histories of philosophy after 1740, among them Johann Brucker’s The History of Philosophy, 6 vol. (1742–67); Johann Buhle’s Lehrbuch der Geschichte der Philosophie, 8 vol. (1796–1804; “Textbook on the History of Philosophy”); Dietrich Tiedemann’s Geist der spekulativen Philosophie von Thales bis Berkeley, 6 vol. (1791–97; “The Spirit of Speculative Philosophy from Thales to Berkeley”); and Gottlieb Tennemann’s Geschichte der Philosophie, 11 vol. (1789–1819; excerpted in A Manual of the History of Philosophy).
Critical Examination Of Reason In Kant
All these developments led directly to the philosophy of Immanuel Kant, the greatest philosopher of the modern period, whose works mark the true culmination of the philosophy of the Enlightenment. Historically speaking, Kant’s great contribution was to elucidate both the sensory and the a priori elements in knowledge and thus to bridge the gap between the extreme rationalism of Leibniz and the extreme empiricism of Hume. But in addition to the brilliant content of his philosophical doctrines, Kant was responsible for three crucial philosophical innovations: (1) a new definition of philosophy, (2) a new conception of philosophical method, and (3) a new structural model for the writing of philosophy.
Kant conceived of reason as being at the very heart of the philosophical enterprise. Philosophy’s sole task, in his view, is to determine what reason can and cannot do. Philosophy, he said, “is the science of the relation of all knowledge to the essential ends of human reason”; its true aim is both constructive (“to outline the system of all knowledge arising from pure reason”) and critical (“to expose the illusions of a reason that forgets its limits”). Philosophy is thus a calling of great dignity, for its aim is wisdom, and its practitioners are themselves “lawgivers of reason.” But in order for philosophy to be “the science of the highest maxims of reason,” the philosopher must be able to determine the source, the extent, and the validity of human knowledge and the ultimate limits of reason. And these tasks require a special philosophical method.
Sometimes Kant called this the “transcendental method,” but more often the “critical method.” His purpose was to reject the dogmatic assumptions of the rationalist school, and his wish was to return to the semiskeptical position with which Descartes had begun before his dogmatic pretensions to certainty took hold. Kant’s method was to conduct a critical examination of the powers of a priori reason—an inquiry into what reason can achieve when all experience is removed. His method was based on a doctrine that he himself called “a Copernican revolution” in philosophy (by analogy with the shift from geocentrism to heliocentrism in cosmology): the assumption that objects must conform to human knowledge—or to the human apparatus of knowing—rather than that human knowledge must conform to objects. The question then became: What is the exact nature of this knowing apparatus?
Unlike Descartes, Kant could not question that knowledge exists. No one raised in the Enlightenment could doubt, for example, that mathematics and Newtonian physics were real. Kant’s methodological question was rather: How is mathematical and physical knowledge possible? How must human knowledge be structured in order to make these sciences secure? The attempt to answer these questions was the task of Kant’s great work Critique of Pure Reason (1781).
Kant’s aim was to examine reason not merely in one of its domains but in each of its employments according to the threefold structure of the human mind that he had inherited from Wolff. Thus the critical examination of reason in thinking (science) is undertaken in the Critique of Pure Reason, that of reason in willing (ethics) in the Critique of Practical Reason (1788), and that of reason in feeling (aesthetics) in the Critique of Judgment (1790).
Literary Forms
The literary form of Enlightenment philosophizing was simple and straightforward. Except for an occasional reversion to the dialogue form, as in Berkeley’s Three Dialogues Between Hylas and Philonous (1713) and in Hume’s Dialogues Concerning Natural Religion (1779), it consisted of inquiries, discourses, treatises, dissertations, and essays, generally well written in clear, relatively nontechnical prose. But Kant not only introduced a formidable technical philosophical terminology into his works but was, in fact, the originator of a new philosophical form—the “critique” or “critical examination”—that had its own special architectonics. Each of Kant’s three critiques is divided into the same three parts: (1) an “analytic,” or analysis of reason’s right functioning, (2) a “dialectic,” or logic of error, showing the pitfalls into which a careless reason falls, and (3) a “methodology,” an arrangement of rules for practice. It is a form that was unique to Kant, but it raised certain problems of “oppositional” thinking, to which 19th-century philosophers such as Georg Wilhelm Friedrich Hegel, Arthur Schopenhauer, and Søren Kierkegaard were subsequently to turn.
The 19th century
Kant’s death in 1804 formally marked the end of the Enlightenment. The 19th century ushered in new philosophical problems and new conceptions of what philosophy ought to do. It was a century of great philosophical diversity. In the Renaissance, the chief intellectual fact had been the rise of mathematics and natural science, and the tasks that this fact imposed upon philosophy determined its direction for two centuries. In the Enlightenment, attention had turned to the character of the mind that had so successfully mastered the natural world, and rationalists and empiricists had contended for mastery until the Kantian synthesis. As for the 19th century, however, if one single feature of its thought could be singled out for emphasis, it might be called the discovery of the irrational. But many philosophical schools were present, and they contended with each other in a series of distinct and powerful oppositions: pragmatism against idealism, positivism against irrationalism, Marxism against liberalism.
Western philosophy in the 19th century was influenced by several changes in European and American intellectual culture and society. These changes were chiefly the Romantic Movement of the early 19th century, which was a poetic revolt against reason in favour of feeling (see Romanticism); the maturation of the Industrial Revolution, which caused untold misery as well as prosperity and prompted a multitude of philosophies of social reform; the revolutions of 1848 in Paris, Germany, and Vienna, which reflected stark class divisions and first implanted in the European consciousness the concepts of the bourgeoisie and the proletariat; and, finally, the great surge in biological science following the publication of work by Charles Darwin (1809–82) on the theory of evolution. Romanticism influenced both German idealists and philosophers of irrationalism. Experiences of economic discord and social unrest produced the ameliorative social philosophy of English utilitarianism and the revolutionary doctrines of Karl Marx (1818–83). And the developmental ideas of Darwin provided the prerequisites for American pragmatism.
A synoptic view of Western philosophy in the 19th century reveals an interesting chronology. The early century was dominated by the German school of absolute idealism, whose main representatives were Johann Fichte (1762–1814), Friedrich Schelling (1775–1854), and Georg Wilhelm Friedrich Hegel (1770–1831). The mid-century was marked by a rebirth of interest in science and its methods, as reflected in the work of Auguste Comte (1798–1857) in France and John Stuart Mill (1806–73) in England, and by liberal (Mill) and radical (Marx) social theory. The late century experienced a second flowering of idealism, this time led by the English philosophers T.H. Green (1836–82), F.H. Bradley (1846–1924), and Bernard Bosanquet (1848–1923), and the rise of American pragmatism, represented by Charles Sanders Peirce (1839–1914) and William James (1842–1910). The new philosophies of the irrational, produced by the highly idiosyncratic thinkers Søren Kierkegaard (1813–55), Arthur Schopenhauer (1788–1860), and Friedrich Nietzsche (1844–1900), ran through the century in its entirety.
The Idealism of Fichte, Schelling, and Hegel
The Enlightenment, inspired by the example of natural science, had accepted certain boundaries to human knowledge; that is, it had recognized certain limits to reason’s ability to penetrate ultimate reality because that would require methods that surpass the capabilities of scientific method. In this particular modesty, the philosophies of Hume and Kant were much alike. But in the early 19th century the metaphysical spirit returned in a most ambitious and extravagant form. German idealism reinstated the most speculative pretensions of Leibniz and Spinoza. This development was due in part to the influence of Romanticism but also, and more importantly, to a new alliance of philosophy with religion. It was not a coincidence that all the great German idealists were either former students of theology—Fichte at Jena and Leipzig (1780–84), Schelling and Hegel at the Tübingen seminary (1788–95)—or the sons of Protestant pastors. It is probably this circumstance that gave to German idealism its intensely serious, quasi-religious, and dedicated character.
The consequence of this religious alignment was that philosophical interest shifted from Kant’s Critique of Pure Reason (in which he had attempted to account for natural science and denied the possibility of certainty in metaphysics) to his Critique of Practical Reason (in which he had explored the nature of the moral self) and his Critique of Judgment (in which he had treated of the purposiveness of the universe as a whole). Absolute idealism was based upon three premises:
That the chief datum of philosophy is the human self and its self-consciousness.
That the world as a whole is spiritual through and through—that it is, in fact, something like a cosmic self.
That, in both the self and the world, it is not primarily the intellectual element that counts but, rather, the volitional and the moral.
Thus, for idealistic metaphysics, the primary task of philosophy was understanding the self, self-consciousness, and the spiritual universe.
The philosophies of Fichte, Schelling, and Hegel had much in common. Fichte, professor of philosophy at the newly founded University of Berlin (1809–14), combined in a workable unity the subjectivism of Descartes, the cosmic monism of Spinoza, and the moral intensity of Kant. He conceived of human self-consciousness as the primary metaphysical fact through the analysis of which the philosopher finds his way to the cosmic totality that is “the Absolute.” Just as the moral will is the chief characteristic of the self, so it is also the activating principle of the world. Thus Fichte provided a new definition of philosophizing that made it the most dignified of intellectual pursuits. The sole task of philosophy is “the clarification of consciousness,” and the highest degree of self-consciousness is achieved by philosophers because they alone recognize “Mind,” or “Spirit,” as the central principle of reality.
This line of thought was carried further by Georg Wilhelm Friedrich Hegel, Fichte’s successor at Berlin and perhaps the single most comprehensive and influential thinker of the 19th century. Kant’s problem had been the critical examination of reason’s role in human experience. For Hegel, too, the function of philosophy is to discover the place of reason in nature, in experience, and in reality—to understand the laws according to which reason operates in the world. But whereas Kant had found reason to be the form that mind imposes on the world, Hegel found it to be constitutive of the world itself—not something that mind imposes but something it discovers. Just as Fichte had projected consciousness from mind to reality, so Hegel projected reason. The resulting Hegelian pronouncements—that “the rational is the real” and that “the truth is the whole”—although they express an organic theory of truth and reality, tended to blur the usual distinctions that previous philosophers had made between logic and metaphysics, between subject and object, and between thought and existence; for the basic tenet of idealism, that reality is spiritual, generates just such a vague inclusiveness.
To the Fichtean foundations, however, Hegel added one crucial corollary: that the Absolute, or Whole, which is a concrete universal entity, is not static but undergoes a crucial development over time. Hegel called this evolution “the dialectical process” (see dialectic). By stressing it, Hegel accomplished two things: (1) he indicated that reason itself is not eternal but “historical,” and (2) he thereby gave new meaning and relevance to the changing conditions of human society in history—which added to the philosophical task a cultural dimension that it had not possessed before.
The philosopher’s vocation, in Hegel’s view, is to approach the Absolute through consciousness—to recognize it as Spirit expressing and developing itself (“realizing itself” was his own phrase) in all the manifold facets of human life. Struggle is the essence of spiritual existence, and self-enlargement is its goal. For these reasons, the various branches of intellect and culture, enumerated below, become stages in the unfolding of the “World-Spirit”:
The psychological characteristics of human beings (habit, appetite, judgment) representing “Subjective Spirit.”
Human laws, social arrangements, and political institutions (the family, civil society, the state) expressing “Objective Spirit.”
Human art, religion, and philosophy embodying “Absolute Spirit.”
Therefore, what began in Hegel as a metaphysics of the Absolute ended by becoming a total philosophy of human culture.
Positivism and Social Theory In Comte, Mill, and Marx
The absolute idealists wrote as if the Renaissance methodologists of the sciences had never existed. But if in Germany the empirical and scientific tradition in philosophy lay dormant, in France and England in the middle of the 19th century it was very much alive. In France, Auguste Comte wrote his great philosophical history of science, Cours de philosophie positive (1830–42; “Course of Positive Philosophy”; Eng. trans. The Positive Philosophy of Auguste Comte), in six volumes.
Influenced by Bacon and the entire school of British empiricism, by the doctrine of progress put forward by Turgot and the marquis de Condorcet (1743–94) during the 18th century, and by the very original social reformer Henri de Saint-Simon (1760–1825), Comte called his philosophy “positivism,” by which he meant a philosophy of science so narrow that it denied any validity whatsoever to “knowledge” not derived through the accepted methods of science. But the Cours de philosophie positive made its point not by dialectic but by an appeal to the history of thought, and here Comte presented his two basic ideas:
The notion that the sciences have emerged in strict order, beginning with mathematics and astronomy, followed by physics, chemistry, and biology, and culminating in the new science of sociology, to which Comte was the first to ascribe the name.
The so-called “law of the three stages,” which views thought in every field as passing progressively from superstition to science by first being religious, then abstract, or metaphysical, and finally positive, or scientific.
Comte’s contribution was to initiate an antireligious and an antimetaphysical bias in the philosophy of science that survived into the 20th century.
In mid-19th-century England the chief representative of the empirical tradition from Bacon to Hume was John Stuart Mill. Mill’s theory of knowledge, best represented in his Examination of Sir William Hamilton’s Philosophy (1865), was not particularly original but rather a judicious combination of the doctrines of Berkeley and Hume; it symbolized his mistrust of vague metaphysics, his denial of the a priori element in knowledge, and his determined opposition to any form of intuitionism. It is in his enormously influential A System of Logic (1843), however, that Mill’s chief theoretical ideas are to be found.
This work—as part of its subtitle, the Principles of Evidence and the Methods of Scientific Investigation, indicates—was concerned less with formal logic than with scientific methodology. Mill made here the fundamental distinction between deduction and induction, defined induction as the process for discovering and proving general propositions, and presented his “four methods of experimental inquiry” as the heart of the inductive method. These methods were, in fact, only an enlarged and refined version of Francis Bacon’s “tables of discovery.” But the most significant section of A System of Logic was its conclusion, Book VI, On the Logic of the Moral Sciences.
Mill took the experience of the uniformity of nature as the warrant of induction. Here he reaffirmed the belief of Hume that it is possible to apply the principle of causation and the methods of physical science to moral and social phenomena. These may be so complex as to yield only “conditional predictions,” but in this sense there are “social laws.” Thus Comte and Mill agreed on the possibility of a genuine social science.
Mill’s Logic was extremely influential, and it continued to be taught at Oxford and Cambridge well into the 20th century, but in the end his importance lay less in logic and epistemology than in ethics and political philosophy. Mill was the great apostle of political liberalism in the 19th century, a true follower of John Locke. And, just as Locke and Rousseau had represented the liberal and the radical wings of social theory in the early modern period, so Mill and Karl Marx represented the liberal and radical approaches to social reform 100 years later.
Mill was raised by social reformers—his father, James Mill (1773–1836), and Jeremy Bentham. His social theory was an attempt, by gradual means arrived at democratically, to combat the evils of the Industrial Revolution. His ethics, expressed in his Utilitarianism (1861), followed the formulations of Bentham in finding the end of society to consist in the production of the greatest quantity of happiness for its members, but he gave to Bentham’s cruder (but more consistent) doctrines a humanistic and individualistic slant. Thus, the moral self-development of the individual becomes the ultimate value in Mill’s ethics.
This trend was also expressed in his essays On Liberty (1859) and Considerations on Representative Government (1861). In the former he stated the case for the freedom of the individual against “the tyranny of the majority,” presented strong arguments in favour of complete freedom of thought and discussion, and argued that no state or society has the right to prevent the free development of human individuality. In the latter he provided a classic defense for the principle of representative democracy, asked for the adequate representation of minorities, urged renewed public participation in political action for necessary social reforms, and pointed out the dangers of class-oriented, or special-interest, legislation.
A radical counterbalance to Mill’s liberal ideas was provided by the philosopher, political economist, and revolutionary Karl Marx. Prior to 1848, Marx used the Hegelian idea of estrangement (which Hegel had used in a metaphysical sense) to indicate the alienation of the worker from the enjoyment of the products of his labour, the crass treatment of human labour as a mere commodity and human beings as mere things, and the general dehumanization of individuals in a selfish, profit-seeking capitalist society.
In The Communist Manifesto (1848), which he wrote with his colleague and friend Friedrich Engels (1820–95), Marx yielded to the revolutionary temper of the times by calling for the violent overthrow of the existing social order (as Rousseau had done before the French Revolution). All of history, Marx said, is the struggle between an exploiting minority and an exploited majority, most recently between the bourgeoisie and the proletariat; and he advocated the formation of a Communist Party to stimulate proletarian class consciousness and to encourage the proletarian seizure of power and the institution of a just and democratically managed socialist society. (See communism; socialism.)
Marx’s revolutionary fervour tended to harm his philosophical reputation in the West, and his philosophical achievement remains a matter of controversy. But certain of his ideas (some Hegelian in inspiration, some original) have endured. Among these are:
That society is a moving balance (dialectic) of antithetical forces that produce social change.
That there is no conflict between a rigid economic determinism and a program of revolutionary action.
That ideas (including philosophical theories) are not purely rational and thus cannot be independent of external circumstances but depend upon the nature of the social order in which they arise.
Independent and Irrationalist Movements
At the end of the 19th century there was a flowering of many independent philosophical movements. Although by then Hegel had been nearly forgotten in Germany, a Hegelian renaissance was under way in England, led by T.H. Green, F.H. Bradley, and Bernard Bosanquet. Bradley’s Appearance and Reality (1893) constituted the high-water mark of the rediscovery of Hegel’s dialectical method. In America a strong reaction against idealism fostered the pragmatic movement, led by Charles Sanders Peirce and William James. Peirce, a logician, held that the function of all inquiry is to eradicate doubt and that the meaning of a concept consists of its practical consequences. James transformed Peirce’s pragmatic theory of meaning into a pragmatic theory of truth; in his The Will to Believe (1897), he asserted that human beings have a right to believe even in the face of inconclusive evidence and that, because knowledge is essentially an instrument, the practical consequences of a belief are the real test of its truth: true beliefs are those that work. Meanwhile, in Austria, Franz Brentano (1838–1917), who taught at the University of Vienna from 1874 to 1895, and Alexius Meinong (1853–1920), who taught at Graz, were developing an empirical psychology and a theory of intentional objects (see intention) that were to have considerable influence upon the new movement of phenomenology.
However, it was not any of these late 19th-century developments but rather the emphasis on the irrational, which started almost at the century’s beginning, that gave the philosophy of the period its peculiar flavour. Hegel, despite his commitment to systematic metaphysics, had nevertheless carried on the Enlightenment tradition of faith in human rationality. But soon his influence was challenged from two different directions. The Danish Christian thinker Søren Kierkegaard criticized the logical pretensions of the Hegelian system; and one of his contemporaries, Arthur Schopenhauer, himself a German idealist and constructor of a bold and imaginative system, contradicted Hegel by asserting that the irrational is the truly real.
Kierkegaard’s criticism of Hegel was an appeal to the concrete as against the abstract. He satirized Hegelian rationalism as a perfect example of “the academic in philosophy”—of detached, objective, abstract theorizing and system building that was blind to the realities of human existence and to its subjective, living, emotional character. What a human being requires in life, said Kierkegaard, is not infinite inquiry but the boldness of resolute decision and commitment. The human essence is not to be found in thinking but in the existential conditions of emotional life, in anxiety and despair. The titles of three of Kierkegaard’s books—Fear and Trembling (1843), The Concept of Dread (1844), and The Sickness unto Death (1849)—indicate his preoccupation with states of consciousness quite unlike cognition.
For a short time Schopenhauer competed unsuccessfully with Hegel at the University of Berlin; thereafter he withdrew to spend the rest of his life in battle against academic philosophy. His own system, though orderly and carefully worked out, was expressed in vivid and engaging language. Schopenhauer agreed with Kant that the world of appearances, of phenomena, is governed by the conditions of space, time, and causality. But he held that science, which investigates the phenomenal world, cannot penetrate the real world behind appearances, which is dominated by a strong, blind, striving, universal cosmic Will that expresses itself in the vagaries of human instinct, in sexual striving, and in the wild uncertainties of animal behaviour. Everywhere in nature one sees strife, conflict, and inarticulate impulse; and these, rather than rational processes or intellectual clarity, are humankind’s true points of contact with ultimate reality.
Friedrich Nietzsche, the third member of the irrationalist triumvirate, was a prolific but unsystematic writer, presenting his patchwork of ideas in swift atoms of thought. Nietzsche viewed the task of the philosopher as destroying old values, creating new ideals, and through them erecting a new civilization. He agreed with Schopenhauer that mind is an instrument of instinct to be used in the service of life and power, and he held that illusion is as necessary to human beings as truth. Nietzsche spent much time analyzing emotional states such as resentment, guilt, bad conscience, and self-contempt.
Kierkegaard, Schopenhauer, and Nietzsche provided for the 19th century a new, nonrational conception of human nature, and they viewed the mind not as open to rational introspection but as dark, obscure, hidden, and deep. But above all they initiated a new style of philosophizing. Schopenhauer wrote like an 18th-century essayist, Kierkegaard was a master of the methods of irony and paradox, and Nietzsche used aphorism and epigram in a self-consciously literary manner. For them, the philosopher should be less a crabbed academician than a man of letters.
Contemporary philosophy
Despite the tradition of philosophical professionalism established during the Enlightenment by Wolff and Kant, philosophy in the 19th century was still created largely outside the universities. Comte, Mill, Marx, Kierkegaard, and Schopenhauer were not professors, and only the German idealist school was rooted in academic life. Since the mid-20th century, however, most well-known philosophers have been associated with academia. Philosophers more and more employ a technical vocabulary and deal with specialized problems, and they write not for a broad intellectual public but for one another. Professionalism also has sharpened the divisions between philosophical schools and made the question of what philosophy is and what it ought to be a matter of the sharpest controversy. Philosophy has become extremely self-conscious about its own method and nature.
The most significant divisions in 20th-century philosophy were influenced and intensified by geographic and cultural differences. The tradition of clear logical analysis, inaugurated by Locke and Hume, dominated the English-speaking world, whereas a speculative and broadly historical tradition, begun by Hegel but later diverging radically from him, held sway on the European continent. From the early decades of the century, the substantive as well as stylistic differences between the two approaches—known after World War II as analytic and Continental philosophy, respectively—gradually became more pronounced, and until the 1990s few serious attempts were made to find common ground between them.
Other less-significant currents in 20th-century philosophy were the speculative philosophies of Henri Bergson (1859–1941) of France, John Dewey (1859–1952) of the United States, and Alfred North Whitehead (1861–1947) of England—each of whom evades easy classification—and the philosophical Marxism practiced in the Soviet Union and eastern Europe until the collapse of communism there in 1990–91.
Bergson, Dewey, and Whitehead
In his An Introduction to Metaphysics (1903) and in his masterpiece, Creative Evolution (1907), Bergson distinguished between two profoundly different ways of knowing: the method of analysis, which is characteristic of science, and the method of intuition, a kind of intellectual sympathy through which it is possible to enter into objects and other persons and identify with them. All basic metaphysical truths, Bergson held, are grasped by philosophical intuition. This is how one comes to know one’s deepest self and the essence of all living things, which he called “duration,” as well as the “vital spirit,” which is the mysterious creative agency in the world.
For Whitehead, philosophy is primarily metaphysics, or “speculative philosophy,” which he described as the effort “to frame a coherent, logical, necessary system of general ideas in terms of which every element of our experience can be interpreted.” Whitehead’s philosophy was thus an attempt to survey the world with a large generality of understanding, an end toward which his great trilogy, Science and the Modern World (1925), Process and Reality (1929), and Adventures of Ideas (1933), was directed.
Whereas Bergson and Whitehead were principally metaphysicians and philosophers of culture, Dewey was a generalist who stressed the unity, interrelationship, and organicity of all forms of philosophical knowledge. He is chiefly notable for the fact that his conception of philosophy stressed so powerfully the notions of practicality and moral purpose. One of the guiding aims of Dewey’s philosophizing was the effort to find the same warranted assertibility for ethical and political judgements as for scientific ones. Philosophy, he said, should be oriented not to professional pride but to human need.
Dewey’s approach to the social problems of the 20th century, unlike that of Vladimir Lenin (1870–1924), emphasized not revolution but the continuous application of the intellect to social affairs. He believed in social planning—in conscious, intelligent intervention to produce desirable social change—and he proposed a new “experimentalism” as a guide to enlightened public action to promote the aims of a democratic community. His pragmatic social theory is the first major political philosophy produced by modern liberal democracy.
Marxist thought
The framework of 19th-century Marxism, augmented by philosophical suggestions from Lenin, served as the starting point of all philosophizing in the Soviet Union and its eastern European satellites. Much of Lenin’s thinking was also devoted to more practical issues, however, such as tactics of violence and the role of the Communist Party in bringing about and consolidating the proletarian revolution. Later Marxism continued this practical concern, largely because it retained the basic Marxist conception of what philosophy is and ought to be. Marxism (like pragmatism) assimilated theoretical issues to practical needs. It asserted the basic unity of theory and practice by finding that the function of the former was to serve the latter. Marx and Lenin both held that theory was always, in fact, expressive of class interests; consequently, they wished philosophy to be transformed into a tool for furthering the class struggle. The task of philosophy was not abstractly to discover the truth but concretely to forge the intellectual weapons of the proletariat. Thus, philosophy became inseparable from ideology.
Analytic philosophy
It is difficult to give a precise definition of analytic philosophy since it is not so much a specific doctrine as an overlapping set of approaches to problems. Its 20th-century origin is often attributed to the work of the English philosopher G.E. Moore (1873–1958). In Principia Ethica (1903), Moore argued that the predicate good, which defines the sphere of ethics, is “simple, unanalyzable, and indefinable.” His contention was that many of the difficulties in ethics, and indeed in philosophy generally, arise from an “attempt to answer questions, without first discovering precisely what question it is which you desire to answer.” These questions thus require analysis for their clarification. Philosophers in this tradition generally have agreed with Moore that the purpose of analysis is the clarification of thought. Their varied methods have included the creation of symbolic languages as well as the close examination of ordinary speech, and the objects to be clarified have ranged from concepts to natural laws and from notions that belong to the physical sciences—such as mass, force, and testability—to ordinary terms such as responsibility and see. From its inception, analytic philosophy also has been highly problem-oriented. There is probably no major philosophical problem that its practitioners have failed to address.
The development of analytic philosophy was significantly influenced by the creation of symbolic (or mathematical) logic at the beginning of the century (see formal logic). Although there are anticipations of this kind of logic in the Stoics, its modern forms are without exact parallel in Western thought, a fact that is made apparent by its close affinities with mathematics and science. Many philosophers thus regarded the combination of logic and science as a model that philosophical inquiry should follow, though others rejected the model or minimized its usefulness for dealing with philosophical problems. The 20th century thus witnessed the development of two diverse streams of analysis, one of them emphasizing formal (logical) techniques and the other informal (ordinary-language) ones. There were, of course, many philosophers whose work was influenced by both approaches. Although analysis can in principle be applied to any subject matter, its central focus for most of the century was language, especially the notions of meaning and reference. Ethics, aesthetics, religion, and law also were fields of interest, though to a lesser degree. In the last quarter of the century there was a profound shift in emphasis from the topics of meaning and reference to issues about the human mind, including the nature of mental processes such as thinking, judging, perceiving, believing, and intending, as well as the products or objects of such processes, including representations, meanings, and visual images. At the same time, intensive work continued on the theory of reference, and the results obtained in that domain were transferred to the analysis of mind. Both formalist and informalist approaches exhibited this shift in interest.

The Formalist Tradition

Logical atomism
The first major development in the formalist tradition was a metaphysical theory known as logical atomism, which was derived from work in mathematical logic by the English philosopher Bertrand Russell (1872–1970). Russell’s work, in turn, was based in part on early notebooks written before World War I by his former pupil Ludwig Wittgenstein (1889–1953). In The Philosophy of Logical Atomism, a monograph published in 1918, Russell gave credit to Wittgenstein for supplying “many of the theories” contained in it. Wittgenstein had joined the Austrian army when the war broke out, and Russell had been out of contact with him ever since. Wittgenstein thus did not become aware of Russell’s version of logical atomism until after the war. Wittgenstein’s polished and very sophisticated version appeared in the Tractatus Logico-Philosophicus, which he wrote during the war but did not publish until 1922.
Both Russell and Wittgenstein believed that mathematical logic could reveal the basic structure of reality, a structure that is hidden beneath the cloak of ordinary language. In their view, the new logic showed that the world is made up of simple, or “atomic,” facts, which in turn are made up of particular objects. Atomic facts are complex, mind-independent features of reality, such as the fact that a particular rock is white or the fact that the Moon is a satellite of the Earth. As Wittgenstein says in the Tractatus, “The world is determined by the facts, and by their being all the facts.” Both Russell and Wittgenstein held that the basic propositions of logic, which Wittgenstein called “elementary propositions,” refer to atomic facts. There is thus an immediate connection between formal languages, such as the logical system of Russell’s Principia Mathematica (written with Alfred North Whitehead and published between 1910 and 1913), and the structure of the real world: elementary propositions represent atomic facts, which are constituted by particular objects, which are the meanings of logically proper names. Russell differed from Wittgenstein in that he held that the meanings of proper names are “sense data,” or immediate perceptual experiences, rather than particular objects. Further, for Wittgenstein but not for Russell, elementary propositions are connected to the world by being structurally isomorphic to atomic facts—i.e., by being a “picture” of them. Wittgenstein’s view thus came to be known as the “picture theory” of meaning.
Logical atomism rested upon a number of theses. It was realistic, as distinct from idealistic, in its contention that there are mind-independent facts. But it presupposed that language is mind-dependent—i.e., that language would not exist unless there were sentient beings who used sounds and marks to refer and to communicate. Logical atomism was thus a dualistic metaphysics that described both the structure of the world and the conditions that any particular language must satisfy in order to represent it. Although its career was brief, its guiding principle—that philosophy should be scientific and grounded in mathematical logic—was widely acknowledged throughout the century.
Logical positivism
Logical positivism was developed in the early 1920s by a group of Austrian intellectuals, mostly scientists and mathematicians, who named their association the Wiener Kreis (Vienna Circle). The logical positivists accepted the logical atomist conception of philosophy as properly scientific and grounded in mathematical logic. By “scientific,” however, they had in mind the classical empiricism handed down from Locke and Hume, in particular the view that all factual knowledge is based on experience. Unlike logical atomists, the logical positivists held that only logic, mathematics, and the special sciences can make statements that are meaningful, or cognitively significant. They thus regarded metaphysical, religious, ethical, literary, and aesthetic pronouncements as literally nonsense. Significantly, because logical atomism was a metaphysics purporting to convey true information about the structure of reality, it too was disavowed. The positivists also held that there is a fundamental distinction to be made between “analytic” statements (such as “All husbands are married”), which can be known to be true independently of any experience, and “synthetic” statements (such as “It is raining now”), which are knowable only through observation.
The main proponents of logical positivism—Rudolf Carnap, Herbert Feigl, Philipp Frank, and Gustav Bergmann—all immigrated to the United States from Germany and Austria to escape Nazism. Their influence on American philosophy was profound, and, with various modifications, logical positivism was still a vital force on the American scene at the beginning of the 21st century.
Naturalized epistemology
The philosophical psychology and philosophy of mind developed since the 1950s by the American philosopher Willard Van Orman Quine (1908–2000), known generally as naturalized epistemology, was influenced both by Russell’s work in logic and by logical positivism. Quine’s philosophy forms a comprehensive system that is scientistic, empiricist, and behaviourist (see behaviourism). Indeed, for Quine, the basic task of an empiricist philosophy is simply to describe how our scientific theories about the world—as well as our prescientific, or intuitive, picture of it—are derived from experience. As he wrote:
The stimulation of his sensory receptors is all the evidence anybody has had to go on, ultimately, in arriving at his picture of the world. Why not just see how this construction really proceeds? Why not settle for psychology?
Although Quine shared the logical postivists’ scientism and empiricism, he crucially differed from them in rejecting the traditional analytic-synthetic distinction. For Quine, this distinction is ill-founded because it is not required by any adequate psychological account of how scientific (or prescientific) theories are formulated. Quine’s views had an enormous impact on analytic philosophy, and until his death at the end of the century he was generally regarded as the dominant figure in the movement.
Identity theory, functionalism, and eliminative materialism
Logical positivism and naturalized epistemology were forms of materialism. Beginning about 1970, these approaches were applied to the human mind, giving rise to three general viewpoints: identity theory, functionalism, and eliminative materialism. Identity theory is the view that mental states are identical to physical states of the brain. According to functionalism, a particular mental state is any type of (physical) state that plays a certain causal role with respect to other mental and physical states. For example, pain can be functionally defined as any state that is an effect of events such as cuts and burns and that is a cause of mental states such as fear and behaviour such as saying “Ouch!” Eliminative materialism is the view that the familiar categories of “folk psychology”—such as belief, intention, and desire—do not refer to anything real. In other words, there are no such things as beliefs, intentions, or desires; instead, there is simply neural activity in the brain. According to the eliminative materialist, a modern scientific account of the mind no more requires the categories of folk psychology than modern chemistry requires the discarded notion of phlogiston. A complete account of human mental experience can be achieved simply by describing how the brain operates.
The Informalist Tradition
Generally speaking, philosophers in the informalist tradition viewed philosophy as an autonomous activity that should acknowledge the importance of logic and science but not treat either or both as models for dealing with conceptual problems. The 20th century witnessed the development of three such approaches, each of which had sustained influence: common sense philosophy, ordinary language philosophy, and speech act theory.
Common sense philosophy
Originating as a reaction against the forms of idealism and skepticism that were prevalent in England at about the turn of the 20th century, the first major work of common sense philosophy was Moore’s paper A Defense of Common Sense (1925). Against skepticism, Moore argued that he and other human beings have known many propositions about the world to be true with certainty. Among these propositions are: “The Earth has existed for many years” and “Many human beings have existed in the past and some still exist.” Because skepticism maintains that nobody knows any proposition to be true, it can be dismissed. Furthermore, because these propositions entail the existence of material objects, idealism, according to which the world is wholly mental, can also be rejected. Moore called this outlook “the common sense view of the world,” and he insisted that any philosophical system whose propositions contravene it can be rejected out of hand without further analysis.
Ordinary language philosophy
The two major proponents of ordinary language philosophy were the English philosophers Gilbert Ryle (1900–76) and J.L. Austin (1911–60). Both held, though for different reasons, that philosophical problems frequently arise through a misuse or misunderstanding of ordinary speech. In The Concept of Mind (1949), Ryle argued that the traditional conception of the human mind—that it is an invisible, ghostlike entity occupying a physical body—is based on what he called a “category mistake.” The mistake is to interpret the term mind as though it were analogous to the term body and thus to assume that both terms denote entities, one visible (body) and the other invisible (mind). His diagnosis of this error involved an elaborate description of how mental epithets actually work in ordinary speech. To speak of intelligence, for example, is to describe how human beings respond to certain kinds of problematic situations. Despite the behaviourist flavour of his analyses, Ryle insisted that he was not a behaviourist and that he was instead “charting the logical geography” of the mental concepts used in everyday life.
Austin’s emphasis was somewhat different. In a celebrated paper, A Plea for Excuses (1956), he explained that the appeal to ordinary language in philosophy should be regarded as the first word but not the last word. That is, one should be sensitive to the nuances of everyday speech in approaching conceptual problems, but in certain circumstances everyday speech can, and should, be augmented by technical concepts. According to the “first-word” principle, because certain distinctions have been drawn in ordinary language for eons—e.g., males from females, friends from enemies, and so forth—one can conclude not only that the drawing of such distinctions is essential to everyday life but also that such distinctions are more than merely verbal. They pick out, or discriminate, actual features of the world. Starting from this principle, Austin dealt with major philosophical difficulties, such as the problem of other minds, the nature of truth, and the nature of responsibility.
Speech act theory
Austin was also the creator of one of the most original philosophical theories of the 20th century: speech act theory. A speech act is an utterance that is grammatically similar to a statement but is neither true nor false, though it is perfectly meaningful. For example, the utterance “I do,” performed in the normal circumstances of marrying, is neither true nor false. It is not a statement but an action—a speech act—the primary effect of which is to complete the marriage ceremony. Similar considerations apply to utterances such as “I christen thee the Joseph Stalin,” performed in the normal circumstances of christening a ship. Austin called such utterances “performatives” in order to indicate that, in making them, one is not only saying something but also doing something.
The theory of speech acts was, in effect, a profound criticism of the positivist thesis that every meaningful sentence is either true or false. The positivist view, according to Austin, embodies a “descriptive fallacy,” in the sense that it treats the descriptive function of language as primary and more or less ignores other functions. Austin’s account of speech acts was thus a corrective to that tendency.
After Austin’s death in 1960, speech act theory was deepened and refined by his American student John R. Searle. In The Construction of Social Reality (1995), Searle argued that many social and political institutions are created through speech acts. Money, for example, is created through a declaration by a government to the effect that pieces of paper or metal of a certain manufacture and design are to count as money. Many institutions, such as banks, universities, and police departments, are social entities created through similar speech acts. Searle’s development of speech act theory was thus an unexpected extension of the philosophy of language into social and political theory.
Continental philosophy
Analytic philosophy had comparatively little influence on the European continent, where the speculative and historical tradition remained strong. Dominated by phenomenology and existentialism during the first half of the 20th century, after World War II Continental philosophy came to embrace increasingly far-reaching structuralist and post-structuralist critiques of metaphysics and philosophical rationality.
The Phenomenology of Husserl and Heidegger
Considered the father of phenomenology, Edmund Husserl (1859–1938), a German mathematician-turned-philosopher, was an extremely complicated and technical thinker whose views changed considerably over the years. His chief contributions were the phenomenological method, which he developed early in his career, and the concept of the “life-world,” which appeared only in his later writings. As a technique of phenomenological analysis, the phenomenological method was to make possible “a descriptive account of the essential structures of the directly given.” It was to isolate and lay bare the intrinsic structure of conscious experience by focusing the philosopher’s attention on the pure data of consciousness, uncontaminated by metaphysical theories or scientific or empirical assumptions of any kind. Husserl’s concept of the life-world is similarly concerned with immediate experience. It is the individual’s personal world as he directly experiences it, with the ego at the centre and with all of its vital and emotional colourings.
With the appearance of the Jahrbuch für Philosophie und phänomenologische Forschung (1913–30; “Annual for Philosophical and Phenomenological Research”) under Husserl’s chief editorship, his philosophy flowered into an international movement. Its most notable adherent was Martin Heidegger (1889–1976), whose masterpiece, Being and Time, appeared in the Jahrbuch in 1927. The influence of the phenomenological method is clear in Heidegger’s work; throughout his startlingly original investigations of human existence—with their unique dimensions of “being-in-the-world,” dread, care, and “being-toward-death”—Heidegger adheres to the phenomenological principle that philosophy is not empirical but is the strictly self-evident insight into the structure of experience. Later, the French philosophical psychologist Maurice Merleau-Ponty (1908–61), building on the concept of the life-world, used the notions of the lived body and its “facticity” to create a hierarchy of human-lived experience.
The Existentialism of Jaspers and Sartre
Existentialism, true to its roots in Kierkegaard and Nietzsche, was oriented toward two major themes: the analysis of human existence, or Being, and the centrality of human choice. Thus its chief theoretical energies were devoted to ontology and decision.
Existentialism as a philosophy of human existence was best expressed in the work of the German philosopher Karl Jaspers (1883–1969), who came to philosophy from medicine and psychology. For Jaspers as for Dewey, the aim of philosophy is practical. But whereas for Dewey philosophy is to guide human action, for Jaspers its purpose is the revelation of Being, “the illumination of existence,” the answering of the questions of what human beings are and what they can become. This illumination is achieved, and Being is revealed most profoundly, through the experience of “extreme” situations that define the human condition—conflict, guilt, suffering, and death. It is through a confrontation with these extremes that the individual realizes his existential humanity.
The chief representative of existentialism as a philosophy of human decision was the French philosopher and man of letters Jean-Paul Sartre (1905–80). Sartre too was concerned with Being and with the dread experienced before the threat of Nothingness. But he found the essence of this Being in liberty—in freedom of choice and the duty of self-determination. He therefore devoted much effort to describing the human tendency toward “bad faith,” reflected in perverse attempts to deny one’s own responsibility and to flee from the truth of one’s inescapable freedom. Sartre did not overlook the legitimate obstacles to freedom presented by the facts of place, past, environment, society, and death. However, he demanded that one surmount these limitations through acts of conscious decision, for only in acts of freedom does human existence achieve authenticity. In The Second Sex (1949), Simone de Beauvoir (1908–86), Sartre’s fellow philosopher and lifelong companion, attempted to mobilize the existentialist concept of freedom for the ends of modern feminism.
After World War II Sartre came to believe that his philosophy of freedom had wrongly ignored problems of social justice, and in his later work, especially the Critique of Dialectical Reason (1960), he sought to reconcile existentialism with Marxism.
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