The engaging and infuriating figure of the early dialogues of Plato, Socrates represented the turning point in Greek philosophy, at which the self-critical reflection on the nature of our concepts and our reasoning emerged as a major concern, alongside cosmological speculation and enquiry. The historical Socrates cannot easily be distinguished from the Platonic character, as there are few other sources for Socrates’s life and doctrines (Xenophon is one). He served as a soldier in the Peloponnesian War, and was married to Xanthippe, by whom he had three male children. He was of strong build, great endurance, and completely indifferent to wealth and luxury.

His subordination of all other concerns to a life spent inquiring after wisdom is the most commanding example, seldom approached, of the proper way of living for a philosopher. He remains the model of a great teacher, but it is uncertain whether he had anything in the nature of a formal school. His friendship with some of the aristocratic party in Athens is often supposed to explain why he was eventually brought to trial, on charges of introducing strange gods and corrupting the youth. Plato’s Crito and Phaedo record the inspirational manner in which he refused to break the laws of Athens and escape during the thirty days between his trial and execution, and they celebrate the fortitude with which he met his death. Whilst his skill at the dialectical, questioning method is unquestioned, his positive contributions and doctrines are matters of some debate, and opinions vary between ascribing to him many of the positive doctrines of Plato, and denying that he had any doctrines at all of his own, apart from his attachment to rigorous dialectical method as the instrument for separating truth from error. All the Greek schools of philosophy conceived of themselves as owing much to Socrates, except for the Epicureans who disliked him intensely, calling him ‘the Athenian buffoon’.