Thucydides was the first ancient Greek historian to double as a social scientist. He set out to understand human events entirely in human terms, without recourse to myth. He sought to know why people go to war and how they are affected by its violence. He studied the civil war in Corcyra, which began when radicals burst into the council house and killed leaders who favored democracy. The strengths and weaknesses of democracy are a major theme of his History . Its larger story shows how the Athenians tried to expand their empire too far and came to a crushing defeat. Here are vivid stories of...