The Socratic Turn addresses the question of whether we can acquire genuine knowledge of good and evil, right and wrong. Reputedly, Socrates was the first philosopher to make the attempt. But Socrates was a materialistic natural scientist in his youth, and it was only much later in life--after he had rejected materialistic natural science--that he finally turned, around the age of forty, to the examination of ordinary moral and political opinions, or to moral-political philosophy so understood.

Through a consideration of Plato's account of Socrates' intellectual development,...