Thought to be the son of a stone-mason, this famous Athenian philosopher believed in teaching through encouraging and challenging others to question their beliefs, preconceptions and prejudices.

He wrote nothing himself: it is mainly through Plato's early dialogues and Xenophon's memoirs that we know about his teaching methods and personality. He condemned the often glib, ready-made rules for success as offered by the Sophists, and regarded it as his duty to shake people out of ill-founded complacency.

He was condemned to death in Athens in 399BC, aged 70, and forced to drink hemlock.