Greek philosophers
Xenocrates
Xenocrates was a Greek philosopher and mathematician. He was born in 398 BC (Chalkédón, today's Kadıköy in Istanbul) and died in 314 BC (Athens).
Xenocrates was a disciple of Plato, and from 339 to 314 BC he headed the (Old) Academy, replacing Speusippus.
He tried to combine the Pythagorean doctrine of numbers and Plato's doctrine of ideas. He said that numbers and ideas were based on one primordial foundation. He distinguished three kinds of being, namely, thought, belief and sense perception. He is said to have separated logic and philosophy and physics and ethics.
His work has not survived.