The gentle philosopher Socrates casts a towering shadow over Western thought. He accounted himself the least knowledgeable of men—one of his most famous sayings states, “All I know is that I know nothing.” But his awareness of his ignorance made him the wisest of men. In the early dialogues of his disciple Plato, Socrates is shown wandering about Athens interrogating men who seemed to have substantial knowledge of ethics, religion, justice or philosophy. He asks questions designed to point out the rickety foundations of these men’s supposed knowledge, imploring them to think of firmer foundations for such knowledge. In some cases Socrates’s interlocutors walk away in disgust from these hard questions. In the end, the city sentences Socrates to death for being such a pest, a “gadfly” stinging a lazy horse, in Socrates’s own metaphor.
Socrates showed how doubt can be marshaled against poorly constructed ideas and arguments, revealing unexamined assumptions at their root. His goal was to establish firm and well-warranted knowledge about important topics that could withstand close questioning. He used doubt as a corrosive agent to burn away sloppy thinking, leaving clear and well-examined thinking to provide a better foundation for genuine knowledge. With his methodology, Socrates paved the path of modern inquiry in the sciences and humanities.