Aristotle

Aristotle came to Athens as a teenager to study under Plato and stayed for twenty years, the brightest student the Academy ever held. But where his teacher gazed toward perfect, unseen forms, Aristotle turned his eyes downward, to the world itself — to fish and bees, weather and motion, friendship and government, the beating logic of a good argument. He wanted not to escape the changing world but to understand it, piece by patient piece.

He more or less invented the idea of organized knowledge. He laid down the first formal system of logic, classified living things, theorized about physics and the heavens, and wrote works on ethics, politics, poetry, and the soul that were studied as authority for two thousand years. For a time he tutored a boy who would become Alexander the Great, and later founded his own school, the Lyceum, where he taught while walking, his students trailing behind.

When Athens turned against him near the end, he withdrew rather than let the city, as he put it, sin twice against philosophy. We honor him as the first great scientist of the West — the encyclopedic mind who believed that everything, from a tragedy to a tide pool, rewards careful, honest looking, and that happiness is found in living well and reasoning clearly.