Born in Athens at the peak of the Athenian civilization. Aeschylus, Sophocles and Euripides were his contemporaries. He served for several years as a soldier. As a member of the Athenian Senate, he refused to connive in the murder of political enemies of the Government and was later brought to trial on a false charge of "introducing new religious practices and corrupting the young". He was sentenced to death. Socrates was acclaimed as the greatest of the Greek philosophers and thinkers.

Greek thinker and founder of Western philosophy. Socrates committed none of his thinkings to writing. It was only through his pupil Plato that we know his ideas. And it is difficult in the later Plato to distinguish between his own thoughts and those of Socrates.

Socrates lived in Athens, where he questioned fellow citizens on how they should live their lives. 'Know thyself' was his principal axiom, and he believe in the unity of beauty, truth and virtue. It was impossible, Socrates held, to know what was good and not pursue it.

Socrates, the first great Athenian philosopher, taught that the key to a good life lay in moral worth and the practice of virtue, and saw it as his duty to make other citizens aware of the ignorance of the true good.

Socrates wrote nothing down; all we know of his teaching comes from the philosophy of his pupil Plato, who was not quite 30 when Socrates was put to death.

All Plato's major works are in dialogue form, and the main speaker is usually Socrates. It is assumed that in the earlier dialogues this character is the real historical Socrates, while in the later ones he represents Plato's mature development of the teachings of Socrates. The continuity of thought makes it impossible to tell where Socrates leaves off and Plato begins.

Throughout his career Plato remained convinced by the teachings of Socrates, and continued to identify virtue with knowledge. However, the corresponding belief - that evil is inevitably done by the ignorant was probably the basis of Plato's distrust of democracy, for a democracy had convicted Socrates.

Socrates thought all wrongdoing was due to ignorance. But in trying to make his fellow citizens aware of their ignorance, he incurred much personal resentment; this led to his trial and conviction on a charge of impiety and corrupting the young with his teaching.

Awaiting execution he continued to discuss philosophy with his friends and pupils. He refused to take advantage of a plan for his escape, electing instead to drink the hemlock handed to him by the executioner.

Plato was so shocked by the death of Socrates that he abandoned the political career he had planned, developing a distrust of Greek democracy which was reflected in much of his political philosophy.

• The New International Illustrated Encyclopaedia, Volume 6, 1954

• Library of Essential Knowledge, Volume 2, Readers Digest, 1980

• Pictorial Knowledge, Volume 10, circa 1950, Newnes