Near the end of the prologue of Plato’s Republic, Socrates says to his opponent Thrasymachus that what they are discussing is “no ordinary/insignificant matter, but how we ought to live” (1.352d). As in many of Plato’s writings, Socrates here played the role of his mouthpiece: “How we ought to live” was indeed no insignificant matter for Plato, but the starting point and ultimate purpose of his philosophical investigations. Relegating the pre-Socratic philosophers to the discipline’s prehistory, it is sometimes suggested that Western philosophy started with Plato. Alfred North Whitehead even claimed that the history of Western philosophy “consists of a...