Aristotle

Born in Stagira, trained at Plato's Academy for twenty years, then tutor to the young Alexander who would conquer the world, Aristotle became perhaps history's most influential thinker. He invented formal logic, founded biology as a science (dissecting over 500 species), wrote the foundational texts of ethics, politics, physics, metaphysics, rhetoric, and poetics. Where Plato looked to abstract Forms, Aristotle looked at the world before him: the oak tree, the city-state, the human being striving for flourishing (eudaimonia). His golden mean taught that virtue lies between extremes; his four causes showed how to truly explain anything. For two millennia, to study philosophy meant to study Aristotle.