Aristotle

Aristotle (384-322 B.C.) was a student at Plato's Academy for twenty years, but he gradually came to reject Plato's philosophy in favor of his own. He felt that Plato's theory of Forms was wrong to deny the reality of change, and so he developed his doctrine of the Four Causes in order to explain change. His work covered the whole range of human knowledge. He invented formal logic and the separate sciences of biology, astronomy, physics, and psychology. He introduced such basic distinctions- as matter and form. substance and accident, and actual and potential. He wrote on politics. poetry and drama, and in his Nichomachean Ethics he argued that virtue was a mean between extremes-the famous "Golden Mean."

His influence on the thought of the ancient world, his revival by the Arab philosophers of medieval times, and his incorporation into Christianity by St. Thomas Aquinas, place Aristotle in the first rank of those who have shaped western civilization. Dante, in the Divine Comedy, called him simply "the master of those who know." He was tutor to Alexander the Great, who conquered the ancient world by the age of 20. Legend has it that Aristotle considered Alexander one of his failures.