Philosophy is an abstract, intellectual discourse–in Greek, φιλοσοφία philosophia means "love of wisdom"–that has attracted many of the brightest minds throughout history, asking questions about the nature of reality and how human beings should live in that reality, and critically analyzing attempts to answer these questions.
What does philosophy mean?
Philosophy, both the field and the concept, is notoriously hard to define. In the past, philosophy has included a number of subjects which have subsequently grown into their own disciplines: the Greek philosopher Aristotle was one of the first biologists and scientists, but it wasn't until later that these became disciplines of their own. In the nineteenth century, what became psychology was a philosophical sub-discipline. Even as these fields have become independent of philosophy, they often raise interesting philosophical questions, and many in philosophy ask similar questions to those in the disciplines philosophy has given rise to, and attempt to figure out the grounding of these new disciplines.
One approach to understanding the meaning of philosophy is to give examples of philosophy. G.E. Moore is said to have answered the question "what is philosophy?" by gesturing at his bookshelves and saying: "It is what these are all about." Similarly, a good start at defining "philosophy" would be to explain that it is the main subject of the works of Plato, Aristotle, Confucius, Lao Tse, Augustine, Thomas Aquinas, Thomas Hobbes, René Descartes, Baruch Spinoza, Gottfried Leibniz, John Locke, David Hume, George Berkeley, Immanuel Kant, Georg Wilhelm Friedrich Hegel, Søren Kierkegaard, John Stuart Mill, Friedrich Nietzsche, Bertrand Russell, Ludwig Wittgenstein, and Martin Heidegger—to omit many more recent names. Any such list, though, would be of necessity partial, and would raise further questions; in the case of most of those mentioned above, for example, some of their published works are not philosophical, so that the list is only really of use if one already understands what is and what is not philosophy.
An alternative approach is to list the main topics discussed by philosophers: any such list would include metaphysics, logic, the philosophy of language, the philosophy of mind, epistemology, the philosophy of science, ethics, political philosophy, and aesthetics. This has the advantage of emphasising the general and abstract nature of most of the subjects of philosophising, but again, any such list will raise further questions; any item in the list either explicitly relies upon understanding of the term "philosophy", or does so implicitly by raising the question as to what is a philosophical treatment as opposed to a non-philosophical treatment of, for example, ethics.
Another way to understand philosophy is to examine its historical development. The Greek word was philosophia (φιλοσοφία), meaning "love of wisdom". ("Philo-" comes from the Greek word philein, meaning to love, and "-sophy" comes from the sophia, or wisdom.) The word philosophos (φιλόσοφος) was first used by Pythagoras to distinguish himself as a seeker of wisdom from those who thought of themselves as the wise (sophos; σοφός). By the time of Socrates the word had come to mean something more like "scientific man" or "learned man". However, the problem with this approach is that the subject itself has changed through history. Originally its scope included all fields of study, other than history, the arts, and professional disciplines such as law; as recently as the nineteenth century, what we now call "science" was called "natural philosophy." In the last two centuries in particular, however, "philosophy" has come to mean an especially abstract, nonexperimental intellectual endeavor.
A fourth approach offers more promise. Instead of a list of practitioners and their works, or of the topics that they discuss, we can describe the distinctive techniques of philosophy: what is it that Plato, Descartes, et al. do in their discussions of metaphysics, ethics, etc., which is distinctively philosophical? Very roughly, we might say it is the study of, or wise reflection about, very general things. To elaborate, we might say that philosophy is the study of the meaning and justification of beliefs about the most general, or universal, aspects of things—a study which is carried out not by experimentation or careful observation, but instead typically by formulating problems carefully, offering solutions to them, giving arguments for the solutions, and engaging in dialectic about all of the above. Philosophers study a huge range of general concepts, such as existence, goodness, knowledge, and beauty. They ask questions such as "What is the good life?" and "Is knowledge even possible?" And while philosophers do not conduct experiments, they study the methods and foundational concepts of experimental disciplines, such as the scientific method, evidence in law, and life.
In many fields of study—consider the numerous sub-disciplines of the physical and biological sciences, for example—pressing and fundamental questions arise that the methods and approaches of the sciences themselves cannot engage. Those questions, and the metaquestion why the sciences cannot answer them, enter the realm of philosophy. Even where it seems likely that as-yet unanswered questions can yield to scientific inquiry, the question how science should proceed in such inquiry may require philosophical debate. Force may equal mass times the first derivative of velocity with respect to time, but what do we mean by time? The sciences have budded off from philosophy, but have left in their bud-bed questions and problems that working alone they could not solve.
Popularly, the word "philosophy" is often used to mean any form of wisdom, or any person's perspective on life (as in "philosophy of life") or basic principles behind or method of achieving something (as in "my philosophy about driving on highways"). That is different from the academic meaning, and it is the academic meaning which is used here.
A brief historical introduction to some leading problems of philosophy
The history of philosophy is vast. There is no way to make sense of it in a few paragraphs; what follows is an abbreviated narrative of a few important strands. This will perhaps give the reader some sense of who some major thinkers were, and what some important philosophical problems were like. Much has been omitted, and we make no claims that these are the most important figures and problems.
Ancient philosophy: what things are, and a focus on virtue
Western philosophy is generally said to have begun with Thales (sixth century B.C.), the first thinker on record to offer a secular answer to a very general question, "What is the first principle, or essential nature, of all things?" We might find Thales' answer, Water, to be strange or amusing, but his achievement lay in asking a general question and offering a secular answer. This began a debate--a strand of what is known as pre-Socratic philosophy, because it predates Socrates--about the ultimate nature (Gk. phusis, φυσις) of things. For instance, Anaximander held this ultimate nature to be The Indefinite; Anaximenes held it to be Air. Such one-word answers are uninformative as summaries of their views, but they show that thinkers did have competing notions of what everything is, ultimately, or in other words, what the ultimate origin and substance of things is. This tradition marked the beginnings of philosophy and of what we now call physics.
Many philosophers accord Socrates (469–399 B.C.) pride of place as the first great Western philosopher. His great achievement, like that of the pre-Socratics, lay not in any particular doctrine, but instead a type of question, and a method of answering it. Socrates reportedly made a habit of questioning the leading Athenian intellects of the day, asking them for a definition or account (the logos) of what they claimed to know about. For example, he asked a famous general, Laches, "What is courage?" Laches offered a definition, to which Socrates would offer a counterexample; the process would repeat until the expert gave up. Socrates, then, would conclude that the person lacked the knowledge that he claimed to have, because genuine knowledge of a thing required the ability to give an account of it. Thus began the central concern of philosophers with the analysis, or offering definitions, of "big" concepts such as virtue and knowledge. The idea is that if we could clarify our basic concepts, we might gain a deep understanding of the way the world really is.
Socrates was most exercised with the nature of the good life and of the virtues, such as justice, piety, temperance, and wisdom. His student Plato (c. 427-347 B.C.) took up these ethical concerns. Plato's master work, The Republic, is an elaborate answer to the question, "What is justice?" In answering this question, Plato develops a theory about what goodness is. We cannot say that goodness is any particular good thing, nor is it a collection of all the good things. It seemed to Plato that goodness is something apart from all of its instances. Furthermore, when we have knowledge of goodness--the knowledge of the account or definition of goodness, which Socrates sought--we need not know any particular instance of goodness, but instead something that exists independently of the various instances. What we know is, therefore, the Form of the Good--something "abstract" or general, which has a sort of heavenly existence independent of the messy, uncertain world of particular things. "Heavenly existence" is not mere poetic license either: Plato held the Form of the Good to be God. However that might be, this brings us to one of the most difficult problems of philosophy: the Problem of Universals (see Metaphysics). There are many ways of approaching this problem, but the reader might get some sense of it by asking: "What sort of thing is goodness, anyway?"
Plato in turn was the teacher of Aristotle (384-322 B.C.), who had a different approach to the Problem of Universals. Whereas Plato asserted the existence of independent, heavenly Forms, Aristotle was much more oriented toward the here-and-now. For Aristotle, goodness is not something over and above what can be found in each good thing; goodness never exists apart from good things, it is merely a quality that can be found in each. This reflects Aristotle's empiricism--his focus on what can be known, through sense-perception, of the world of particular things we live in. Plato, by contrast, is regarded as the first representative of rationalism, since he thought that genuine knowledge was not of particular things, but only of abstract Forms like goodness, and could be secured only by rational reflection on our concepts of the Forms. Aristotle wrote voluminously about a vast array of subjects, from what we now call philosophy, to biology, rhetoric, and much more.
Plato and Aristotle each established schools of philosophy--Plato, the famous Academy, members of which were called Academics, and Aristotle, the Lyceum, members of which were called Peripatetics. Other schools arose as well: Epicureanism and Stoicism, which Romans embraced heartily, and which included a strand called Cynicism. These schools--collectively known as Hellenistic philosophy--flourished in Greece and Rome from the fourth century B.C. until the third century A.D.
The Eastern dimension of philosophy
Despite the pretensions of some philosophers to objectivity and rationality, the key figures and movements in the history of philosophy depends on who you ask. In France, the list of pivotal figures is very different from that in Germany, which is very different from that in Britain, which is very different from that in the United States. Each country, in fact, tends to favor "its own" philosophers in a perhaps insular way. But the most marked divide in the history of philosophy is between "East and West." Most accounts in English will insist that philosophy, as the structured, rational discussion of great issues such as the origins of the universe, the nature of right and wrong, and the essence of human existence started in ancient Greece. Some are capable of disputing this, holding that philosophy started in the East and flourished in North Africa before eventually taking root in Western Europe. The first Chinese philosophers, Lao Tzu and Confucius, were contemporaries of the first Greek philosophers such as Thales and Parmenides, but the earliest Indian philosophers greatly predate these.
What influence the earliest Eastern philosophy might have had on Western philosophy, if any, is shrouded in obscurity. Plato's dialogues drew in part upon Pythagoras, who in turn may have drawn upon the Eastern philosophers. As one Western commentator notes:
The cosmological doctrines of the Pythagoreans have an affinity with views of which traces survive in many parts of the world. Thus, in China, a system of musical sounds is related to the order of the universe and with the orderly sequence of the seasons. In India the sound OM is the creative principle of the universe; the Vedic chants maintain cosmic stability and compel even the gods." 
However, the key Chinese philosophers, Confucius, Lao Tzu and Chuang Tzu are barely known or discussed outside their native China. Many of the great philosophical schools were formulated during the Spring and Autumn Period and Warring States Period, and came to be known as the Hundred Schools of Thought. The four most influential of these were Confucianism, Taoism, Mohism, and Legalism. Later on, during the Tang Dynasty, Buddhism from India also became a prominent philosophical and religious discipline. Eastern thought is often contrasted with Western philosophy, and criticised for not offering a clear distinction between philosophy and religion, yet, of course, up until the nineteenth century Western philosophy was presented, at least on the face of it, as a search by believers for knowledge of God. Like Western philosophy, Chinese philosophy covers a broad and complex range of thought, possessing a multitude of schools that address every branch and subject area of philosophy.
Much of this page, therefore, must be acknowledged as a Western perspective, indeed more narrowly, an Anglo-American perspective on the term "philosophy."
Medieval philosophy: reason meets religion
Many of the secular philosophical interests of the Greeks fell by the wayside as intellectual life--and the story of philosophy--moved into the protected walls of medieval monasteries. Medieval philosophy included not just Christian monks, such as St. Augustine of Hippo, St. Anselm of Canterbury, and St. Thomas Aquinas, but Jewish philosophers such as Maimonides (Moshe ben Maimon) and Gersonides (Levi ben Gershon), and Islamic philosophers such as Avicenna (Ibn Sina) and Averroës (Ibn Rushd). These philosophers had, in fact, wide-ranging philosophical interests. But if these religiously inclined philosophers had a chief aim, it was to systematize and, to some extent, rationalize the faith of the Church.
St. Anselm of Canterbury (1033-1109) lived as the Dark Ages were coming to an end. His most famous achievement was in his Proslogion, the ontological argument for the existence of God, which went like this. Anselm invites us to conceive "that than which nothing greater can be thought." In other words, imagine anything at all, from a pebble to a dog to the Milky Way Galaxy; whatever you imagine, try to imagine something greater. Then we say: the greatest thing imaginable would be "that than which nothing greater can be thought." Anselm considered that the "fool" of Psalms (14:1), who said, "There is no God," must have this concept. Even if he was an atheist, he had this concept of that than which nothing greater can be conceived. But, in fact, there is a greater concept than the atheist's, namely, the concept of a being that actually exists. We do have this concept of the greatest conceivable being, and to be really the greatest conceivable, that being must exist. This is God. Anselm thought we merely had to think about the implications of a concept, and it would be clear that the thing we conceive of--God--actually exists.
In a way, Anselm followed Plato: as we said earlier, Plato conceived of the role of philosophy as being the rational drawing out of conclusions from Ideas. By contrast, St. Thomas Aquinas (1225-74) took his cues from the works of Aristotle, recently rediscovered to Christians (but long known to Islamic scholars).
In fact, in his Summa Theologica, Aquinas, not long after rejecting Anselm's argument, most famously offered "Five Ways" to prove the existence of God, which are, arguably, arguments from experience, or what philosophers call a posteriori arguments. For instance, he said that we observe that the world is ordered into causes and effects, with one thing causing another, which causes another--making very long chains of causes and effects. But it is impossible that there be an endless chain of causes, Aquinas said, because then there would be no ultimate (final) explanation of any "link" in the chain. So there had to be a first cause; and this is God.
Not all philosophers (or theologians) have held that the existence of God can be proven. Some of these, in fact, are atheists, and believe that there are serious problems with these and all arguments for the existence of God; but some of them are fideists (from Latin fides), meaning that they believe we cannot justify the existence of God rationally, but we are nevertheless justified in believing through faith. Blaise Pascal exemplifies this in Pascal's Wager: simply put, given that we cannot know whether God exists, there is the possibility that God either exists or doesn't, and there is the choice between believing and not believing. If you believe and God exists, you get the reward of heaven; if you believe and God does not exist, you get nothing. If you don't believe and God exists, you get the punishment of hell; if not, you get nothing. The person who believes in God and is wrong loses little according to Pascal - a few hours each week in church and in prayer. Faced with these choices, Pascal suggests that you would be justified in trying to believe in God simply because of the possible outcomes. The idea that faith has some priority over reason later emerges in the form of the religious existentialism of writers like Søren Kierkegaard - see Christian existentialism.
Modern philosophy: everything must be doubted
Modern philosophy is usually said to have begun with René Descartes, but several factors predating Descartes were instrumental in the decline of medieval philosophy. Political thinkers like Niccolo Machiavelli and Thomas Hobbes challenged aspects of the divine right of Kings. Scientists like Nicolaus Copernicus and Galileo Galilei challenged the Church-supported geocentric model of the universe. Other religious thinkers, like Desiderius Erasmus, openly criticized Church institutions. It was in this cultural milieu that Descartes began his program of radical skepticism.
In Descartes' Mediations, he examines his beliefs and discards those which it was possible to doubt. In this way, he demonstrated how our sense experience of the external world can be doubted: we could be dreaming everything up for example, or an evil demon could be deceiving our senses. However, this method also demonstrated that there is one belief that is undoubtable: that we exist, that there must be an "I" doing the doubting. Descartes then employs a version of the ontological argument to demonstrate the existence of God, and then to conclude that since God is not a deceiver, we can be certain of our beliefs in the external world.
Against Descartes, John Locke proposed the idea that all knowledge comes from sense experience. Immanuel Kant attempted to synthesize the rationalist approach of Descartes with the empiricism of Locke and Bishop George Berkeley. In the nineteenth century, philosophy moved in an idealistic direction with Georg Wilhelm Friedrich Hegel. Hegel's ideas became foundational for Karl Marx, and became a starting point for critique by Søren Kierkegaard. The style of philosophy pioneered by Kierkegaard, Arthur Schopenhauer and Friedrich Nietzsche is fundamentally different from many who went before: it is at times sarcastic, witty and attempts to convince readers through rhetoric and misdirection - in these authors, you will not find any symbolic logic or carefully argued premises and conclusions. This tradition is an important part of what has come to be called Continental philosophy - encompassing, in the twentieth century, the phenomenology of Edmund Husserl and Maurice Merleau-Ponty, the existentialism of Jean-Paul Sartre and Albert Camus, as well as the work of Marx and psychoanalysts Sigmund Freud and Carl Jung.
In the twentieth century, philosophy took what has been described as a "linguistic turn" - that is, it saw it's object as being primarily the understanding of language, and the relationship between language and thought. The work of Ludwig Wittgenstein and Martin Heidegger heralded this approach, with the former showing the shortcomings of the representationalist-referential theory of language - that is, the idea that linguistic elements point to a common reference point, which Wittgenstein's earlier work - the Tractatus Logico-Philosophicus - along with Bertrand Russell and Gottlob Frege advocated. In philosophy since, a great number of philosophical questions have been revisited and reframed linguistically - for instance, the question of whether or not one can believe in God has been rethought of as whether or not one participates in a religious language game (see Don Cupitt). Similarly, questions about descriptive ethics have been reframed as whether or not ethical language is meaningful. On the Continental side of philosophy, language has been understood through a variety of critical apparatuses: Ferdinand de Saussure's structuralism, the reactions to that known as post-structuralism, and the developments of postmodernism and critical theory. Such an approach to philosophy has been widely criticized as obscurantist and often bordering on irrationalism.
The analytic, linguistic "turn" of Russell, Frege and Wittgenstein has been influential in much of contemporary philosophy, which has become extremely logical and technical. The leading examples of this kind of philosophy include Donald Davidson, Saul Kripke, Derek Parfit, Michael Dummett, Wilfrid Sellars, Willard Van Orman Quine, Hilary Putnam, Jerry Fodor, David Armstrong, David Lewis, Paul Grice, Alfred Tarski, Edmund Gettier and so on.
The role of philosophy
Main article: Applied Philosophy
Philosophy has applications. The most obvious applications are those in ethics, applied ethics in particular and in political philosophy. The political philosophies of John Locke, Jean-Jacques Rousseau, Karl Marx, and John Stuart Mill have shaped and been used to justify governments and their actions: Locke, among others, on the American founding fathers, Marx on socialism and Communism, John Rawls in the early days of Tony Blair's New Labour, and Robert Nozick on the libertarian right. Philosophy of education deserves special mention, as well; progressive education as championed by John Dewey has had a profound impact on educational practices in the United States in the twentieth century.
Other important, but less immediate applications can be found in epistemology, which might help one to regulate one's notions of what knowledge, evidence, and justified belief are. Philosophy of science discusses the underpinnings of the scientific method, among other topics sometimes useful to scientists (philosophers of science like Michael Ruse and Robert Pennock have appeared as expert witnesses in American court cases over creationism). Aesthetics can help to interpret discussions of art, and has had inspirational value for some artists. Even ontology, surely the most abstract and least practical-seeming branch of philosophy, has had important consequences for logic and computer science. In general, the various "philosophies of," such as philosophy of law, can provide workers in their respective fields with a deeper understanding of the theoretical or conceptual underpinnings of their fields.
Moreover, recently, there has been developing a burgeoning profession devoted to applying philosophy to the problems of ordinary life: philosophical counseling. The idea of philosophy as a way to happiness has it's roots in the writings of the Platonist philosopher Boethius and his text, the Consolations of Philosophy.
In recent years, a great number of books have come out that have tried to provide philosophical reflection on and around topics of popular culture - movies like The Matrix have served as hooks for philosophers to discuss everything from abstract metaphysics through to applied ethics and social theory. Just as with popular science, there are a number of writers actively writing books about philosophy for consumption by non-philosophers, and these seem to be selling better than ever.
- quoted by Antony Flew in his preface to the first edition of A Dictionary of Philosophy (1979)
- This usage is still to be found in the names of departments, courses, and chairs in some Universities, e.g., the University of Cambridge and the University of Glasgow.
- A. P. Cavendish in A Critical History of Western Philosophy ed D. J. O'Connor, p7, Macmillan 1985
- Summa Theologica, Part I, Q. 2, Art. 1, Objection 2
- Summa Theologica, Part I, Q. 2, Art. 3
- Aquinas explicitly grounds in experience all five of the Five Ways. Even his modal argument begins, "We find in nature things that are possible to be and not to be, since they are found to be generated, and to corrupt, and consequently, they are possible to be and not to be." (Summa Theologica, Part I, Q. 2, Art. 3)