In an age when philosophers had scarcely glimpsed the horizons of the mind, a boy named Aristocles decided to forgo his ambitions as a wrestler. Adopting the nickname Plato, he embarked instead on a life in philosophy. In 387 B.C. he founded the Academy, the world's first university, and taught his students that all we see is not reality but merely a reproduction of the true source. And in his famous Republic, he described the politics of “the highest...

The "Long Debate" on the nature of truth, the scale of real values, the life one should aspire to live, the character of justice, the sources of law, and the terms of civic and political life is encompassed by the name philosophy. Three persistent themes--understood as problems--are knowledge, conduct, and governance, on which there is a storehouse of insights, some so utterly persuasive as to have shaped thought itself. Beginning with Plato and Aristotle,...