Philosophy is the oldest form of systematic, scholarly inquiry. The name comes from the Greek philosophos, "lover of wisdom." The term, however, has acquired several related meanings: (1) the study of the truths or principles underlying all knowledge, being, and reality; (2) a particular system of philosophical doctrine; (3) the critical evaluation of such fundamental doctrines; (4) the study of the principles of a particular branch of knowledge; (5) a system of principles for guidance in practical affairs; and (6) a philosophical spirit or attitude. All of these meanings of philosophy are recognizable in the intellectual traditions of ancient Greece. The pre-Socratics (see \Tpre-Socratic philosophy\t) sought to find fundamental, natural principles that could explain what individuals know and experience about the world around them. The pre-Socratics and, later, \TPlato\t and \TAristotle\t tried to develop a comprehensive set of principles that would account for their knowledge of both the natural and the human world. In developing philosophies, these early thinkers saw that their reflections could be used as a means of criticizing and often refuting popularly accepted mythological views as well as the thoughts of their predecessors and contemporaries. \TSocrates\t, at his trial, proclaimed a basic philosophical premise, that "the unexamined life was not worth living." By this he meant that if people do not examine and critically evaluate the principles by which they live, they cannot be sure that worthwhile principles exist. As the Greek thinkers codified their pictures of the world, they saw that for each science or study of some aspect of the world there could be a corresponding philosophy of this science or study, such as the philosophies of science, art, history, and so on. Each of these involves examining the fundamental principles of a discipline to see if they are logical, consistent, and--most important--true. Because ancient philosophers questioned the various ways of life by which people live and sought the most satisfactory one, they developed their philosophical attitudes and theories as guides to practical living. From Socrates down to 20th-century thinkers like Bertrand \TRussell\t and Jean Paul \TSartre\t, a major element of the philosophical enterprise has been devoted to trying to designate what constitutes the good life for humans both as individuals and as social and political beings. This kind of concern has contributed to the image of the philosopher as standing aside from and impervious to all the ups and downs of everyday existence. Michel de \TMontaigne\t declared that "to philosophize is to learn to die," indicating that the philosopher can be philosophical even in the face of death. The Stoic thinkers (see \TStoicism\t) are usually seen as the epitome of this sense of philosophy. They maintained their philosophical attitude of calm reflection in the face of all sorts of temporary disasters. PHILOSOPHICAL QUESTIONS Because the term philosophy has various meanings, the nature of the field can be most easily grasped by examining the kinds of problems and questions the field deals with. In the beginnings of Western philosophy, the pre-Socratic thinkers dealt primarily with a metaphysical question: What is the nature of ultimate reality as contrasted to the apparent reality of ordinary experience? They tried to determine whether some ultimate constituents of the world would be the real and basic elements, whereas everything else would be ephemeral and merely a surface appearance. If such a reality existed, would it be permanent and unalterable, or would it be subject to change or alteration like everything else? The pre-Socratics generated some of the basic problems involved in defining reality, that is, in finding something so basic that it cannot be explained by anything else. They found their attempts to present logical explanations of their metaphysical theories ran into paradoxical results. Could a permanent, unchanging reality account for a changing world? \TZeno of Elea\t became famous for working out his paradoxes, which claimed nothing could really change or move. Some of his paradoxes and some of those connected with the Greek \Tatomism\t still play a role in modern theoretical physics. Over time, some aspects of the attempt to delineate reality became separated from the metaphysical quest and became the subject matter of the various natural sciences. This development has accelerated since the 17th century. The areas of study that have been peeled off from philosophy and assigned to the natural sciences include astronomy, physics, chemistry, geology, biology, psychology, and others. An example of this process may be seen in the consideration of a major metaphysical question, the relationship of mind and body. Originally, Platonic metaphysics claimed that the body and the mind were two separate and distinct entities. Plato, in fact, claimed the body was the prison house of the soul or mind. In the 17th century, Rene \TDescartes\t contended that mind and body were two separate and distinct substances that had nothing in common although they interact. Several Indian schools of philosophy hold a similar view. In the West this problem was gradually taken over by psychologists and neurophysiologists. The present tendency is to reduce mental phenomena to brain phenomena and thereby reduce the problem from a mind-body problem to a body problem. Another constant philosophical question, from Greek times up to the present, has been to try to establish the difference between appearance and reality. Once people learned about sense illusions, the question arose of how to tell what seems to be from what really is. Skeptical thinkers have pressed the claim that no satisfactory standard can be found that will actually work for distinguishing the real from the apparent in all cases. On the other hand, various philosophers have proposed many such criteria, none of which has been universally accepted. Another type of question raised by philosophers is: What is truth? Various statements about aspects of the world seem to be true, at least at certain times. Yet experience teaches that statements that have seemed to be true have later had to be qualified or denied. Skeptics have suggested that no evidence would be able to tell, beyond any show of doubt, that a given statement is in reality true. In the face of such a challenge, philosophers have sought to find a criterion of truth, especially a criterion of truth that would not be open to skeptical challenge. Philosophers have also traditionally raised questions about values: What is good? How can good be distinguished from bad or evil? What is justice? What would a just society be like? What is beauty? How can the beautiful be distinguished from the ugly? These questions all deal with matters of evaluation rather than fact. Scientific investigation is of only slight help in determining if abortion is bad or if Vermeer's Milkmaid is a beautiful picture. The values that are at issue are not perceived in the same way as facts. If they were, much more agreement would exist about the specific answers to value questions. The philosopher seeks to find some means of answering these sorts of questions, which are often the most important ones that a person can ask and which will exhibit the basis of a theory of values. PHILOSOPHICAL METHODS In view of the kinds of questions that philosophers deal with, what methods does the philosopher use to seek the answers? The philosopher's tools are basically logical and speculative reasoning. In the Western tradition the development of \Tlogic\t is usually traced to Aristotle, who aimed at constructing valid arguments and also true arguments if true premises could be uncovered. Logic has played an important role in ancient and modern philosophy--that of providing a clarification of the reasoning process and standards by which valid reasoning can be recognized. It has also provided a means of analyzing basic concepts to determine if they are consistent or not. Logic alone, however, is not enough to answer philosophers' questions. It can show when philosophers are being consistent and when their concepts are clear and unambiguous, but it cannot ascertain if the first principles or the premises are correct. Here philosophers sometimes rely on what they call intuition and sometimes on a speculative reasoning process. From their initial premises, philosophers then try to work out a consistent development of their answers to basic philosophical questions, following the rules of logic. Irrationalist philosophers, however, such as the Danish thinker Soren \TKierkegaard\t, have contended that the less logical the solution to philosophical problems, the better. Philosophers such as these sometimes argue that the most important elements of existence and experience cannot be contained by logic, which is, after all, an element of experience itself. The part, they argue, cannot explain the whole. PHILOSOPHY'S RELATION TO OTHER DISCIPLINES Philosophy is both related to most disciplines and yet different from them. Almost from the beginning of both mathematics and philosophy in ancient Greece, relations were seen between them. On the one hand, the philosophers were strongly impressed by the degree of certainty and rigor that appeared to exist in mathematics as compared to any other subject. Some, like the philosopher-mathematician \TPythagoras of Samos\t, felt that mathematics must be the key to understanding reality. Plato claimed that mathematics provided the forms out of which everything was made. Aristotle, on the other hand, held that mathematics was about ideal objects rather than real ones; he held that mathematics could be certain without telling us anything about reality. In more modern times, Descartes and Baruch \TSpinoza\t used mathematics as their model and inspiration for formulating new methods to discover the truth about reality. The philosopher-mathematician Gottfried Wilhelm von \TLeibniz\t, the co-discoverer (with Isaac Newton) of calculus, theorized about constructing an ideal mathematical language in which to state, and mathematically solve, all philosophical problems. Similar views have been advanced in the 20th century as ways of resolving age-old philosophical difficulties. Attempts to accomplish this have found far from unanimous approval, however. Philosophy has both influenced and been influenced by practically all of the sciences. The physical sciences have provided the accepted body of information about the world at any given time. Philosophers have then tried to arrange this information into a meaningful pattern and interpret it, describing what reality might be like. Western philosophers over much of the last 2,500 years have provided basic metaphysical theories for the scientists to fit their data into and as the data changed, their metaphysical interpretations have had to be adjusted. Thus the scientific revolution of the 17th century, encompassing the scientific work of Johannes Kepler, Galileo, and Newton, was accompanied by a metaphysical revolution led by such thinkers as Descartes, Spinoza, and Leibniz. In the late 18th and early 19th centuries, the prevailing philosophers in England and France came to the conclusion that the sciences are, and ought to be, completely independent of traditional metaphysical interpretations. Instead, the sciences should just try to describe and codify observations and experiences. This approach has led in the last two centuries to a divorce of philosophy from the sciences. What has developed in response is a new branch of philosophy, the philosophy of science, which examines the methods of science, the types of scientific evidence, and the ways the sciences progress. A third intellectual area that has been intimately involved with philosophy is religion. In ancient Greece some philosophers like \TAnaxagoras\t and Socrates scandalized their contemporaries by criticizing aspects of Greek religion. Others offered more theoretical approaches about the evidence for the existence and nature of God or the gods. Some denied the existence of a deity. When Christianity entered the Greek world, attempts were made to develop a philosophical understanding of Christianity. Finally, toward the end of the 4th and beginning of the 5th century, Saint \TAugustine\t achieved a synthesis of some of the elements of Platonic philosophy with the essentials of Christianity. Throughout the Middle Ages, philosopher theologians among the Jews, Muslims, and Christians sought to explain their religions in rational terms. They were opposed by antirational theologians who insisted that religion is a matter of faith and belief and not of reasons and arguments. After the Reformation, philosophers like Spinoza and David \THume\t began criticizing the traditional philosophical arguments used by theologians. Hume and Immanuel \TKant\t sought to show that all of the arguments purporting to prove the existence of God and the immortality of the soul were fallacious. Philosophers sought to explain why people were religious on nonrational grounds, such as psychological, economic, or cultural ones. The defenders of religion found themselves estranged from the philosophers, who kept using the latest results of science and historical research to criticize religion. Some, like Kierkegaard, made a virtue of this estrangement, insisting that religious belief is a matter of faith, and therefore not a matter of reason. More recently, since World War II, a group of theologians who are interested in recent philosophical developments and in the relationship between religion and contemporary culture have attempted to discover what religious statements can be intellectually meaningful. The history of the relation between philosophy and theology is thus a long and mixed affair, running the gamut from clarifying religion and providing a justification for it to tearing apart its intellectual underpinnings and trying to see what is left that a 20th-century scientifically oriented person can believe or take seriously. BRANCHES OF PHILOSOPHY The several different branches of philosophy correspond to the different problems being dealt with. One of the most basic is \Tepistemology\t, the theory of knowledge (episteme is Greek for knowledge). It deals with what can be known, how it can be known, and how certain the individual can be about it. It has special branches like the philosophy of science. The kinds of answers that emerge from a particular epistemology usually structure its \Tmetaphysics\t. Metaphysics is the study of nature of reality, the study of what features of experience are real and which are apparent. Aristotle called metaphysics the study of being as such; the term ontology is often used to describe this branch of philosophy today. How a person gets to know about pure being (an epistemological problem) colors what it is that is known. The reverse is also the case. What the individual thinks the world is really like colors what he or she thinks can be known about it. How the individual reasons about the world and how he or she can certify knowledge belongs to the branch of philosophy called logic. Logic provides the rational framework for all philosophical discussion, but is also itself open to metaphysical interpretations about what sort of world it is explaining. Other branches of philosophy such as \Tethics\t, \Taesthetics\t, and political philosophy deal with evaluative aspects of the world such as what is good conduct, what is beautiful, and what is socially and politically just. The proposed answers to these questions are much involved with the philosopher's epistemological and metaphysical theories, and the values the philosopher espouses color his or her epistemology and metaphysics. Sometimes the pursuit of particular aspects of experience (such as sensations) or the use of particular tools (such as the analysis of language) will reorient philosophical inquiry or give birth to new branches of philosophy. Thus philosophy is never reasoned in a vacuum. It is concerned not only with abstract questions; it is also conditioned by history. HISTORY OF WESTERN PHILOSOPHY The Pre-Socratics Western philosophy began in Greece, in the Greek settlement of Miletus in Anatolia. The first known philosophers were \TThales of Miletus\t and his students, \TAnaximander\t and \TAnaximenes\t. Present-day knowledge of this \TMilesian school\t is based on fragments attributed to them by later writers. These first philosophers were metaphysicians, seeking for an element or force behind appearance that explained everything. Thales said that all was ultimately water, Anaximander that it was boundless or the infinite, and Anaximenes that it was air. Subsequent Greek philosophers, such as \THeraclitus\t and \TParmenides\t, argued about whether change or permanence was the basic feature of the world and about whether one or more than one element was the fundamental constituent of reality (see \Tmonism\t; \Tpluralism\t). Greek philosophy before Socrates was principally concerned with these metaphysical questions. Socrates Socrates, an Athenian, was primarily interested in value questions that affected what a person should do. At the time in Athens, the paid teachers, the \TSophists\t, taught people how to live successfully; they did not raise the Socratic question of what was the right way of life, however. Socrates did not write anything, but he is vividly portrayed by his pupil Plato in the Dialogues as being the "gadfly" of Athens, forever asking people why they are doing what they are doing and making people realize that general principles were necessary to justify their conduct. Socrates was finally arrested and accused of heresy and corrupting the young of Athens. Socrates used his trial, described in Plato's Apology, as a final opportunity to make his general point. His accusers, he showed, did not know what the charges actually meant and had no evidence for them. He reported that the Delphic oracle had said that he, Socrates, was the wisest of all of the Athenians. Socrates said he was the wisest because he alone knew nothing and knew that he knew nothing, whereas everybody else thought they knew something. In spite of his eloquence and wisdom, Socrates was convicted and sentenced to death. Plato After Socrates' execution, his disciple Plato developed the first comprehensive philosophical system and founded the Academy, the first formal philosophical school. Plato contended that knowledge must be of universals (that is, of general types or kinds) and not of particulars. To know a particular cat, Miranda, the individual must first know what it is to be feline in general. Otherwise he or she will not be able to recognize the particular feline characteristics in Miranda. These universals, Plato claimed, were the basic elements from which the world was formed. They are called the Forms, or Platonic Ideas. Mathematics provides the most obvious cases of these Forms. They are known not by sense perception but by reasoning. They are known by the mind, not by the bodily organs. The world of Platonic Ideas is the unchanging Forms of things. The philosopher should turn away from this world of appearance and concentrate on the world of Forms. Plato, in his most famous work, The Republic, said that the world would be perfect when philosophers are kings and kings are philosophers. He believed that the philosopher-kings would know what justice really is, and, based on their knowledge of the Forms, they could then achieve justice in all societies. For Plato the ultimate Idea, which illuminated the rest of the pure ideas, was the Idea of the Good. As Plato grew older he became more mystical about this idea. The school of \TNeoplatonism\t, which began a few centuries after his death, stressed these otherworldly and mystical elements, identifying the idea of the Good with God. Aristotle Plato's leading student, Aristotle, developed the most comprehensive philosophical system of ancient times. Aristotle broke with Plato, stressing the importance of explaining the changing world that humankind lives in as opposed to the Platonic Ideas. Aristotle spent years studying the natural sciences and collecting specimens, and about 90 percent of his writings are on scientific subjects, mostly on biological ones. Aristotle believed he could account for the changes and alterations in this world without either having to deny their reality or having to appeal to another world. For Aristotle all natural objects were composed of form and matter, and the changes that take place in matter are the substitution of one form for another. This substitution takes place because every natural object has a goal, or telos, which it is its nature to achieve. Thus stones, because they are essentially material, seek the lowest point, which is why they fall down. Each species is ultimately trying to achieve a state of perfection which for Aristotle was a state of perfect rest. The cosmos, as Aristotle saw it, is an ordered striving for this perfection. The pinnacle of the order is the Unmoved Mover, the ultimate cosmic agent, which fully and perfectly realizes its essence of eternal thought. The heavenly spheres imitate the Unmoved Mover and by so doing set the heavens in an eternal spherical motion; this process is repeated by individual souls, and so on. Aristotle's vision of the Cosmos remained central to Western thought until the time of Nicolaus Copernicus. Hellenistic and Roman Periods In the period from about 300 BC to AD 200 the central philosophical concerns shifted to how an individual should conduct his or her life. The Stoics, the Skeptics (see \Tskepticism\t), and the Epicureans (see \TEpicureanism\t), although they dealt with the classical epistemological and metaphysical issues, emphasized the question of how humans should conduct themselves in a miserable world. All these theories stressed withdrawal, whether physical, emotional, or intellectual, from the turmoils of the day. Medieval Period Greek philosophy was the major formative influence on the later philosophical traditions of Judaism, Islam, and Christianity. In all three, the theories of the Greeks, particularly Plato and Aristotle, were employed to clarify and develop the basic beliefs of the religious traditions. \TPhilo of Alexandria\t introduced Platonic ideas and methods into Jewish thought, particularly into the interpretation of Scripture about the beginning of the Christian era. He exerted little influence on later Jewish thought, however, and the Jewish philosophy of the Middle Ages seems to have developed as a movement parallel to those in Islam. Important figures in early medieval Jewish thought include Isaac Israeli, \TSaadia ben Joseph Gaon\t, and the Neoplatonist Solomon \Tibn Gabirol\t. The most important Jewish thinker of the Middle Ages, however, was \TMaimonides\t. Maimonides developed a comprehensive interpretation of religion and understanding based on Aristotelian principles that was influential in the Christian West as well as among Jewish thinkers. In Judaism, as in Islam and Christianity, religious speculation and philosophy developed in close connection. This development is particularly evident in the Jewish mystical tradition, the \TKabbalah\t. The esoteric teachings of these schools have influenced much later Jewish thought, including that of Spinoza, the most important Jewish philosopher of the early modern period. Drawing both on his religious background and on the geometric method of Descartes, Spinoza developed a philosophical \Tpantheism\t of great depth. In the Islamic tradition as well the starting point was the work of Plato and Aristotle. The 9th-century Neoplatonist al-\TKindi\t was followed by al-\TFarabi\t, who drew on both Plato and Aristotle to create a universal Islamic philosophy. The most important of the medieval Muslim philosophers, however, was Avicenna (ibn Sina). Starting from the distinction between essence and existence, Avicenna developed a metaphysics in which God, the necessary being, is the source of created nature through emanation. Both his metaphysics and his intuitionist theory of knowledge were influential in the later Middle Ages as well as in the later history of Islamic thought. The philosophical tradition did not go unchallenged, however. The 11th-century theologian and mystic al-\TGhazali\t mounted a critique of philosophy, specifically Avicenna's, that is rich in argument and insight. Al-Ghazali's Incoherence of the Philosophers provoked a response by \TAverroes\t ibn Rushd entitled the Incoherence of the Incoherence, in which al-Ghazali's arguments are countered point for point. Averroes was best known, however, as an interpreter of Aristotle and excited great influence on all subsequent thinkers in the Aristotelian tradition. In the later Middle Ages the historian and philosopher \TIbn Khaldun\t produced a trenchant critique of culture, and the elaboration of metaphysics and epistemology was carried on in the theosophical schools of Islamic mysticism. The first systematic Christian philosophy was that of \TOrigen\t, but for the European Middle Ages no authority could rival Saint Augustine. Augustine elaborated a Neoplatonist vision combining the metaphysics of \TPlotinus\t with an elaboration of the Christian doctrine of the Trinity. To this he added an epistemology in which knowledge is achieved through illumination by grace. No substantial movement arose beyond Augustine until the 12th century, when new interest arose in logic and theory of knowledge. In this connection the most important figures are Saint \TAnselm\t and Peter \TAbelard\t. In the late 12th and early 13th centuries the writings of Aristotle were reintroduced into the West, first in translations from the Arabic and later in direct translation. After some initial resistance Aristotle became the dominant philosophical authority and remained so until the Renaissance. First Saint \TAlbertus Magnus\t and then Saint Thomas \TAquinas\t combined Aristotle's philosophy with the tradition of Augustinian theology to produce a synthesis holding that Aristotle was right about those things that are within the grasp of reason, while what was beyond reason could only be known by faith. Thus reason could prove that God exists, but his nature could be known only by faith. More extreme Aristotelian schools developed and came into conflict with the church, which, in 1277, issued condemnations of many positions held by Aristotle and Aquinas, among others. In the 14th century two figures dominated the scene: \TDuns Scotus\t and \TWilliam of Occam\t. Scotus developed an extremely complex philosophy based on a number of earlier positions, and Occam's critiques of metaphysics and epistemology remain paradigms of philosophical argument. Rationalism The synthesis of Christianity and Aristotelianism was a major form of \Tscholasticism\t, which dominated European philosophy into the 17th century. During the Renaissance other forms of ancient philosophy began to be revived and used as ammunition against the scholastics. This involved the Renaissance Platonists and the Skeptics, as well as others interested in esoteric doctrines like that of the Kabbalah. In terms of the future development of philosophy, the revival of ancient skepticism played the greatest role. This view, popularized by Montaigne in the late 16th century, raised the fundamental epistemological problem of what can be known. The methods of the new scientific schools conflicted with, and thus brought into question, the principles inherited from the Middle Ages. Rene Descartes proposed a method for guaranteeing knowledge. He argued that in order to provide a secure foundation for knowledge it was necessary to discover "clear and distinct ideas" that could not be doubted and could serve as a basis for deriving further truths. He found such an idea in the proposition "I think, therefore I am." Using this as a paradigm, Descartes drew a distinction between thinking substance and extended substance, or mind and matter. He went on to draw conclusions about God, nature, and mind that continue to be influential. For this reason Descartes is often considered the founder of modern philosophy. A few years after Descartes's death, Baruch de Spinoza offered his theory to improve on that of Descartes. Spinoza insisted that only one substance, God, exists, and that two of his attributes are thought and extension. Everything that is and that can be known about is an aspect of God. Spinoza's God, however, was the antithesis of the God of traditional religion. God, or Nature (as Spinoza put it), was the laws from which everything followed. In Spinoza's pantheistic world everything had to be what it was, and everything was to be understood rationally. The mind and body were two aspects of the same thing, which was to be understood either logically or in terms of natural science. A third great 17th-century rationalist was Gottfried Wilhelm von Leibniz. The basic unit of his metaphysics, equivalent to a substance, was the monad, a center of force or energy. Each monad was internally determined by its definition. Monads could not interact, but, due to a "preestablished harmony," the action in one monad coincided with that in another. God chose the monads in the world so that it would be the best of all possible worlds. (A world with more or less or different monads would not be as good, or God would have chosen it.) Leibniz believed that the truths about monads could be discovered by rational analysis. Empiricism Descartes, Spinoza, and Leibniz were all rationalists in their epistemologies; they stressed a world of metaphysical truths that could be discovered by reason. In contrast to this kind of philosophizing, a quite different approach developed in Great Britain, stressing the importance of sense experience as the basis of knowledge (see \Tempiricism\t). Starting with Sir Francis \Tbacon\t, the empirical theory of knowledge was propounded both as a way of eliminating various metaphysical and theological difficulties and as a way of genuinely advancing knowledge. The most important statement of this theory was made by John \TLocke\t. He claimed that all knowledge comes from sense experience. Individuals are, however, forced to believe that underlying experience is some indefinable kind of substance. No one can be completely certain of direct intuitive inspections of his or her ideas, less certain of demonstrations from them, and still less certain of what Locke called "sensitive knowledge," knowledge of the reality of experience. In spite of the limitations on knowledge, humans can know enough to function in this world. Bishop George \TBerkeley\t saw Locke's theory as having dangerous skeptical and irreligious tendencies because of its reliance on a material substance for ideas to belong to. Berkeley insisted that the only things truly known are ideas and that ideas can only exist in the minds that perceive them. Matter is simply complexes of sensations. Nothing really exists except perceiving and being perceived (esse est percipere). What holds the world together is that God perceives everything all of the time. Berkeley's \Tidealism\t gained few adherents. If it is granted that all of our knowledge consists only of sense experiences, no evidence exists that the world is any more than ideas and the minds they are in. In philosophy this position is called \Tsolipsism\t, the view that the only reality is the self. Berkeley was followed by David Hume, who showed that a thoroughly consistent empirical theory of knowledge leads to a complete skepticism. Hume's major contribution was to show that an individual cannot gain any causal information about experience, or about what is beyond immediate experience, from empirical knowledge. He or she can neither deduce nor induce the cause or the effect of experience (see \Tcausality\t). Individuals thus have no basis for accepting that the future must resemble the past. It is only habit or custom that leads them to expect and believe that the items found constantly conjoined in experience will remain so in the future. Hume also argued that from empirical data humans could have no real knowledge of substance, mind, or even God. They are reduced to complete skepticism except that habits or customs make them unjustified believers. Kant and Hegel The German philosopher Immanuel Kant claimed that reading Hume awoke him from his dogmatic slumbers and made him realize the depths of the problem of knowledge that cried out for a solution. Kant insisted that humans do possess genuine knowledge. The problem was to show how, in the face of Hume's critique, knowledge was possible. Kant first insisted that although all knowledge begins in experience, this does not mean that all knowledge comes from experience. The human mind provides the forms and the categories which can be used to describe experience. Because these are the necessary conditions of all possible human experience, experience will have certain characteristics. But this knowledge cannot be extended to what is beyond all possible experience--to real substances (things-in-themselves; see \Tnoumenon\t), to the self, or to God. After Kant a new metaphysical movement developed in Germany starting from Kant's claim that the individual contributes the form of all possible experience. Georg Wilhelm Friedrich \THegel\t advanced the idea that the basic element of reality (The Real) is not a principle of organization interior to the mind but a process that acts through individuals and unfolds itself in the history of the world. This universal reason has expressed itself in the various forms of the world's development--from a purely physical stage, to a biological one, to a human one. In the human one, society is developing from ancient tyranny toward freedom in a final rational state, in which all previous contradictory developments will be resolved (see \Tdialectic\t). Hegel worked out a metaphysics in which all of human history was rational. His ideas were influential throughout Europe in the 19th century, particularly on the ideas of Karl \TMarx\t. Hegel's ideas were soon taken up in the United States by Josiah \TRoyce\t and others and in England by idealistic philosophers such as F. H. \TBradley\t. 20th Century Twentieth-century philosophy has been characterized in part by its revolt against Hegelianism. \Tpragmatism\t in the United States and the modern empiricism of Bertrand Russell, \Tlogical positivism\t, and linguistic philosophy in both Britain and America all rejected Hegelian metaphysics. The pragmatists wanted an earthy theory--that the truth is that which works--as an expeditious way of solving problems. From William \TJames\t to John \TDewey\t pragmatism dominated American thought in the first half of this century. Logical positivism, based on modern developments in logic and an empiricism like Hume's, was the joint result of English thinkers like Russell and an Austrian group called the Vienna circle, whose most influential member, Ludwig \TWittgenstein\t, had been a student of Russell's at Cambridge. The English and Austrian positivists and linguistic philosophers challenged any form of metaphysical thinking and insisted that something could be said to be true if (and only if) it could be verified by logical or scientific procedures. No metaphysical claim, they insisted, could meet this test (see \Tanalytic and linguistic philosophy\t). Quite different kinds of philosophy developed in France and Germany. One of the most extreme reactions to Hegel came from the Danish thinker Soren Kierkegaard. Kierkegaard believed that all metaphysical systems are unsuccessful, but that to avoid despair an individual had to opt for some sort of belief, by taking a "leap of faith." Kierkegaard's emphasis on subjectivity, confrontation, and despair has greatly influenced the school of thought called \Texistentialism\t. Although Kierkegaard was a religious Christian, many of those who have used his basic approach are irreligious. Among several important reactions to Kant, the most notable is \Tphenomenology\t, developed by Edmund \THusserl\t. Bracketing questions about the self and other transcendental ideas, Husserl attempted to elaborate a method for the analysis of experience as it presents itself. His most important student, Martin \THeidegger\t, developed a philosophy of "being-in-the world," which has also influenced Jean Paul Sartre and other existentialists. To tell in what direction the mainstream of philosophy will move in the last quarter of the 20th century is impossible at this close range. Richard H. Popkin EASTERN PHILOSOPHY The Indian Tradition The philosophical traditions of India have their beginnings in reflection on the \TVedas\t and specifically in attempts to interpret the \TUpanishads\t. A wide variety of schools emerged including some that specifically reject the authority of the Vedas. Thus the Indian philosophy is commonly divided in two traditions: the orthodox schools of \THinduism\t that accept Vedic authority, and the nonorthodox schools that do not accept that authority. Within the first category are six major schools: Samkhya, Yoga, Vaisheshika, Nyaya, Mimamsa, and Vedanta. The second category consists of Charvaka, Jainism, and Buddhism. Samkhya, one of the oldest and most influential of the schools, is traditionally held to have been founded by Kapila, who may have lived as early as the 7th century BC and to whom the Samkhya-sutra (Principles of Samkhya) is attributed. Samkhya metaphysics is based on the distinction between prakriti and purusha, which may be rendered as the objective, or nature, and the subjective, or self. All objects in the world are essentially constituted by the combination of atoms, which emerge from the eternal and uncaused prakriti. Even the individual ego, or mind, is a result of the constant atomic flux of prakriti. Purusha, on the other hand, is not to be identified with the ego, or mind. It also is uncaused, eternal, and unchanging and underlies the perceived ego. There is a plurality of such selves, which are the loci of consciousness and in conjunction with which prakriti evolves. The bondage to suffering that is the common starting point of all Indian philosophical thought arises from the involvement of purusha with prakriti. Release comes when ignorance is overcome; that the attachment of purusha to the changing empirical world is illusory becomes apparent. The means by which this ignorance is overcome are elaborated by the \Tyoga\t school. While accepting much of the Samkhya position, Yoga, as developed by Patanjali (2d century BC), believes in a supreme self or purusha, identified with the god Isvara. The method of Yoga is to bring the self to understanding by meditation designed to curb the constant changes brought on by involvement in the perceived world. The knowledge acquired through meditation is an intuitive, nonrational, and direct cognition of the nature of things. This intuition is the cessation of individuality and the identity of the self with the eternal purusha. Some form of Yoga is recognized as a practical method of enlightenment by most of the other Indian schools. The Vaisheshika system is thought to have been developed by Kanada in the 3d century BC. The essential aspect of Vaisheshika is a complex pluralistic metaphysics that recognizes nine substances: earth, water, fire, air, ether, space, time, self, and mind. The first four material substances are atomic and give rise to material composite objects. Mind is also atomic but does not give rise to composite objects. Vaisheshika tends to be theistic and sees God as guiding the world in accordance with the law of \Tkarma\t. Human action perpetuates the workings of karma, and thus liberation is achieved through the cessation of action, and achievement of a state beyond pleasure, pain, and experience in general. Nyaya is closely associated with Vaisheshika, and they are often grouped together. The emphasis in Nyaya is on methods of argument, and particularly on the elaboration of logical theory, which is used to justify Vaisheshika metaphysics. Nyaya distinguishes various forms and origins of knowledge, as originally put forward by the school's founder Gantama (2d century BC). In the course of time Nyaya developed a variety of arguments for the existence of God, as conceived by Vaisheshika, some of which parallel the classic arguments in the Western traditions. The Mimamsa is often divided into two main branches, the Purva Mimamsa and the Uttara Mimamsa. The Mimamsa sutra of Jainini dates perhaps from the 4th century BC and begins a tradition in which the two most important later figures are Kumarila Bhatta and Prabhakara, both 7th century AD. The Mimamsa in general is concerned with establishing the nature and demands of religious law or duty (\Tdharma\t) as it is found in the Vedas. As such it tends to emphasize the practical, although Mimamsa thinkers have made important contributions to logic and theory of knowledge. The Mimamsa, particularly the Uttara Mimamsa, is closely associated with \TVedanta\t and sometimes treated simply as a school within the Vedantic tradition. Vedanta means "the end of the Vedas" and in general suggests analysis and contemplation of the theory and vision of the Vedic material. The point of departure for Vedanta is Badarayana's Brahma sutras, also known as the Vedanta sutras. This represents the earliest attempt to organize and explicate the Upanishads and is itself an extremely difficult text, which has served as the object of commentaries by the major figures of later Vedanta schools. Central to these schools is the interpretation of Brahman (see \TBrahma and Brahman\t) and its relation to atman (self). The best known of the schools is the nondualist, or advaita, Vedanta of Shankara (AD 788-820), for whom Brahman is undifferentiated, eternal, and unchanging and the world is illusion, or maya. The modified nondualism, or vishishtadvaita, of Ramanuja (1017-1137) argues for the reality of individual self (atman) and the world but claims that they are dependent on Brahman. The dualist, or dvaita, Vedanta of Madhva (1197-1276) insists on a sharp distinction between Brahman and atman, as well as between Brahman and the world. Of the three nonorthodox schools, the first two can be dealt with briefly. Charvaka is known only from fragments referred to in the works of its opponents. It seems to have been an extreme materialist reaction to the Vedic teachings and to have argued for the primacy of life in the world, the extinction of the individual at death, and perhaps an ethic of personal gratification. \TJainism\t, on the other hand, is an ethical religion that arose in the 6th century BC. It insists on the distinction between matter and soul and argues for a realistic atomism in the context of an atheistic universe. Salvation is achieved through the three jewels of faith, knowledge, and practice of the virtues, which are nonviolence, truth telling, not stealing, chastity, and not being attached to worldly goods and concerns. \TBuddhism\t originated as a sectarian movement in India in the 6th-5th century BC, but it spread over much of China, Southeast Asia, and Japan. In the course of its history Buddhism has developed diverse philosophical traditions. The central teaching of Buddhism is the dharma. This term can mean a variety of things, including "the nature of things," "the law," and "the true view of reality." Dharmas, in the plural, are usually held to be the genuine constituents of reality as opposed to the mere appearance. Common to almost all schools of Buddhist philosophy is the view that all things in the world have their origin in other things, a doctrine known as "dependent coorigination." This doctrine leads in most cases to a metaphysics of flux, usually joined to a pluralistic atomism. Another doctrine common to almost all schools is that of anatta, the denial of a metaphysical self. The doctrine of anatta is often seen as a consequence of dependent coorigination, and the perceived self is analyzed as a bundle of skandhas, the five components of personality. The analysis of these doctrines differed from school to school, however, and within a few centuries of the Buddha's death a variety of positions had developed, traditionally held to have been 18. The two most important divisions were the Mahasanghikas and the Sthaviras, the former identifying with the larger community and the latter claiming to continue the tradition of the elders. Out of these two groups developed Mahayana and Theravada Buddhism, a division that continues to this day. Among the philosophical schools of Theravada are the Pudgalavadins, the Vaibhashika, and the Sautrantika. For the Pudgalavadins the doctrine of anatta proved unacceptable. They themselves were divided into a number of sects but were united in the view that some sort of unifying person (pudgala) must exist as the subject of karmic rebirth and possible salvation. The pudgala served as a principle of identity through time in the context of which the various religious and intellectual doctrines of Buddhism could be said to make sense. The Vaibhashikas (a branch of the Saravastivadin sect), on the other hand, argued that the dharmas, the actual constituents of reality, were identical with those of perceived reality if properly analyzed. The proposed analysis is one of a plurality of events, coordinated by causal laws. Essences and general concepts are merely abstractions, with only a conceptual as opposed to an actual reality. Knowledge, on this view, is a direct perception of real events and objects. The Sautrantikas have much in common with the Vaibhashikas, but they distinguish between a phenomenal world and the world as it really is. Thus the Sautrantikas deny the reality of perceived dharmas. This difference is important in their respective theories of knowledge because, unlike the Vaibhashikas, the Sautrantikas do not say that objects are directly perceived. They are, rather, inferred from the representations of sense imprinted upon the mind through contact with the world. Among the Mahayana schools the Yogacara and the Madhyamika are the two most important. The Yogacara differs markedly from the three schools noted above in arguing that only consciousness is genuinely real and that perceived objects are ultimately illusory. The claim is that, because objects are constituted by instantaneous events, they have no duration and thus cannot be said to exist. The unenlightened consciousness laboring under the law of karma does not realize this, but through the practice of yoga and moral discipline liberation can be achieved, and the identity of the perceived world with consciousness can be grasped. Many scholars hold the Madhyamika to be the central philosophy of Buddhism. The name itself means "traveler on the middle way" and suggests a position that attempts to mediate between the extremes of the other schools. The founder and leading intellect of Madhyamika was Nagarjuna (2d century AD). Nagarjuna mounted a detailed critique of the theory of knowledge that held knowledge to be expressible only in terms of propositions. These propositions are derived from individual concepts and from perceptions and are in some sense a construction of the individual rather than a genuine representation of reality in itself. Understanding is reached when the relativity of these conceptual constructions is recognized and claims to absolute knowledge and truth are given up. The highest wisdom is in seeing this ephemeral relativity and acquiring direct awareness of reality itself, unconditioned by concepts. Many later schools are related to the Madhyamika, including the Zen schools, although the relations are difficult to uncover in many places. The Chinese Tradition Philosophical thought in China has largely concerned itself with social and political philosophy. This assertion is not to say that cosmological and metaphysical speculation has been absent. The I CHING reflects a complicated vision of the universe. The oracles of the I Ching began to assume their present written form perhaps as early as the 7th century BC, and the book as a whole played an important role throughout the subsequent development of Chinese philosophy. The first recognized philosopher in China, however, was \TConfucius\t (541-497 BC). Confucius taught that the goal of the philosopher was to become learned, but this concept means more than merely knowing a large number of facts. Rather, on the basis of a broad learning in the classic texts, the canon of which he essentially formulated, Confucius held that a person, regardless of his or her social status, could become aware of the moral order of the cosmos and of his or her proper place in it. He taught the primacy of the family, and the duties incumbent upon its various members, stressing harmony and unity and the self-evident goodness of the ethical life. This vision has in many ways remained a dominant one in \TConfucianism\t. The recorded sayings of Confucius do not present a systematic vision. The first figure in the Confucian tradition to move toward a philosophical system was \TMencius\t (4th-3d century BC). Mencius argued for the essential goodness of persons--that divergence in moral responsibility is a result of a bad upbringing or environment. The results of a poor moral training can be overcome by education, and society is, thus, essentially perfectible. The duty of government is to foster the well-being of the people and bring society to perfection, a goal with which the genuine ruler is in accord due to his inborn goodness and moral sense. A strain in Confucianism diametrically opposed to the idealism of Mencius arose a generation later in the thought of Hsun-tzu (330-225 BC). Hsun-tzu argued that, far from good, the inborn nature of persons is evil, or uncivil. Rather than eliciting innate moral virtues through education, Hsun-tzu insists on the need to impose them from without. This doctrine has been variously interpreted; such a position leads to the nonabsoluteness of ethical norms and hence leads as much in the direction of liberalism as authoritarianism. Yet another facet of Hsun-tzu's thought is an acute logical sense, and he left a penetrating essay on names and meaning. Until the advent of Neoconfucianism in the medieval period, Hsun-tzu was usually considered a superior thinker to Mencius. The Neoconfucians emphasized an essentialist moral striving based on Confucius, Mencius, and two texts, the Great Learning and Doctrine of the Mean. In its various forms, Neoconfucian thought dominated Chinese learning and social life until the beginning of the 20th century. The second important indigenous Chinese tradition is \TTaoism\t. The teaching of the Tao Te Ching, a work attributed to the semilegendary \TLao-tzu\t (6th century BC), is elusive and complex and can perhaps best be characterized as teaching the eternal principle of reality and the way in which all things are governed by and find their true natures in it. It implies a metaphysics of impermanence and change, and the philosopher who attains a clear vision of the eternal Tao (way) and its relation to this flux acquires happiness and peace. The most important later Taoist philosopher was Chuang-tzu. In \TChuang-tzu\t the Taoist divergence from, and rejection of, the Confucian ideals becomes pronounced. Whereas the Confucian tradition believes in the molding of the person through education, Chuang-tzu saw the classical teachings of the schools as tending to lead the person away from an understanding of the nature of things, the Tao, and thus away from a genuine awareness of his or her own nature and place in the world. This outlook sometimes led to Taoism being seen as antisocial. Nevertheless, both Chuang-tzu and Mencius, who was perhaps his contemporary, saw the goal of philosophy as attaining an awareness of the essential harmony of things, although they disagreed on the origin of this harmony and how awareness is to be attained. Only the two main strands in Chinese thought have been mentioned. The Moists, who taught the existence of a Supreme Spirit that possessed equal and universal love for all people; the Legalists, who advocated a practical philosophy of political domination; and the Buddhists, who became important from the 4th century AD on, also exercised wide influence in Chinese thought. Within the Neoconfucian tradition a variety of positions emerged. In the last century Western philosophical and political thought has entered the Chinese tradition, most importantly Marxism. In Chinese philosophy, as in the other traditions examined, drawing any firm conclusions about the future is impossible. G. S. Davis Bibliography: \TGeneral\t: Edwards, Paul, ed., The Encyclopedia of Philosophy, 8 vols. (1967). \TWestern\t \Tphilosophy\t: Armstrong, A. H., ed., The Cambridge History of Later Greek and Early Medieval Philosophy (1967); Blau, J. L., The Story of Jewish Philosophy (1962); Brumbaugh, R. 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