Plato was born 427 BC in Athens, Greece.
He seems as a young man to have been set on a political career. The excesses of Athenian political life seem to have persuaded him to give up political ambitions. In particular, the execution of Socrates in 399 BC had a profound effect on him.
Plato left Athens after his master, Socrates, had been executed and travelled in Egypt, Sicily and Italy. In Egypt he learnt of a water clock and introduced it into Greece. In Italy he learned of the work of Pythagoras and came to appreciate the value of mathematics. On his return to Athens he founded, on land which had belonged to Academos, a school of learning which being situated in the grove of Academos was called the Academy.
Plato presided over his Academy in Athens, an institution devoted to research and instruction in philosophy and the sciences, from 387 BC until his death.
All important mathematical work of the 4th century BC was done by friends and pupils of Plato. Although he made no important mathematical discoveries himself, his belief that mathematics provides the finest training for the mind was extremely important in the development of the subject.
Over the door of the Academy was written:
Let no one unversed in geometry enter here .
Plato concentrated on the idea of 'proof' and insisted on accurate definitions and clear hypotheses. This laid the foundations for Euclid's systematic approach to mathematics.
His beliefs as regards the universe were that the stars, planets, Sun and Moon move round the Earth in crystalline spheres. The sphere of the Moon was closest to the Earth, then the sphere of the Sun, then Mercury, Venus, Mars, Jupiter, Saturn and furthest away was the sphere of the stars. He believed that the Moon shines by reflected sunlight.
Plato died 347 BC in Athens, Greece. His Academy flourished until 529 AD when it was closed down by the Christian Emperor Justinian who claimed it was a pagan establishment.