Western Philosophy is generally said to begin in the Greek cities of western Asia Minor (Ionia) with Thales of Miletus, who was active around 585 B.C. and left us the opaque dictum, "All is water." His most noted students were Anaximenes of Miletus ("All is air") and Anaximander.

Other thinkers and schools appeared throughout Greece over the next couple of centuries. Among the most important were Heraclitus ("All is fire", all is chaotic and transitory), Anaxagoras (reality is so ordered that it must be in all respects governed by Mind), the Pluralists and Atomists (the world is composite of innumerable interacting parts), the Eleatics Parmenides and Zeno (All is One and change is impossible), the Sophists (became known (perhaps unjustly) for claiming that truth was no more than opinion and for teaching people to argue fallaciously to prove whatever conclusions they wished). This whole movement gradually became more concentrated in Athens, which had become the dominant city-state in Greece.

There is considerable discussion about why Athenian culture encouraged philosophy, but one popular theory says that it occurred because Athens had a direct democracy. It is known from Plato's writings that many sophists maintained schools of debate, were respected members of society, and were well paid by their students. It is also well known that orators had a tremendous influence on Athenian history, possibly even causing its failure (See Battle of Lade). One other theory for the popularity of philosophical debate in Athens was due to the use of slavery there - the workforce, mainly slaves, performed the labour that otherwise would have been taken up by the male population of the city. Freed from working in the fields or in productive activity, they were then free to engage in the assemblies of Athens and spend long hours discussing popular philosophical questions. The theory fills in the blanks by saying that the Sophists' students wanted to acquire the skills of oration in order to influence the Athenian Assembly, and thereby grow wealthy and respected. Since winning debates led to wealth, the subjects and methods of debate became highly developed.

The key figure in transforming Greek philosophy into a unified and continuous project - the one still being pursued today - is Socrates, who studied under several Sophists. He then spent much of his life engaging everyone in Athens in a discussion to try to determine whether anyone had a good idea of what they were talking about, especially when they talked about important matters like justice, beauty and truth. He wrote nothing, but inspired many disciples. He was executed in 399 B.C. on the charge that philosophy and sophistry, interchangeably, was destroying the piety and moral fiber of the city.



His most important student was Plato, who founded the Academy of Athens and wrote a number of philosophical dialogues using his master's methods of inquiry to examine problems. Central ideas are the Theory of Forms, that the mind is imbued with an innate capacity to understand and apply concepts to the world, and that these concepts are in a significant way more real, or more basically real, than the things of the world around us; the immortality of the soul, and the idea that it too is more important than the body; the idea that evil is a kind of ignorance, that only knowledge can lead to virtue, that art should be subordinate to moral purposes, and that society should be ruled by a class of philosopher kings. In the later dialogues Socrates figures less prominently, and the Theory of Forms is cast in doubt; more directly ethical questions become the focus. Interestingly, in his most famous work, The Republic, Plato critiques democracy, condemns tyranny, and he proposed instead a three tiered structure of society, with workers, guardians and philosophers, in an equal relationship , where no innocents would ever be put to death again. Citing the philosophers greater knowledge of the forms as the reason for them being more appropriate in running society.

Plato's most outstanding student was Aristotle, perhaps the first truly systematic philosopher. Aristotelian logic was the first type of logic to attempt to categorize every valid syllogism. A syllogism is a form of argument that is guaranteed to be accepted, because it is known (by all educated persons) to be valid. A crucial assumption in Aristotelian logic is that it has to be about real objects. Two of Aristotle's syllogisms are invalid to modern eyes. For example, "All A are B. All A are C. Therefore, some B are C." This syllogism fails if set A is empty, but there are real members of set B.