At the center of The History of the Peloponnesian War is Thucydides’ application of a rational, empirical method for analyzing human events and their outcomes. Though his methods do not reflect those of contemporary historians, his commitment to seeking causes in human actionsas well as in the natural world and happenstance (whether helpful or harmful) represented a radical shift from the standards of his time. For this reason, he is considered one of the fathers of history.

In the ancient Greece of Thucydides’ time, people believed that gods engineered positive or negative outcomes, they relied on divination to determine their courses of action, and fate was immutable and predetermined. For example, in Homer’s epic poems, which Thucydides references, the Trojans in The Iliad were fated to lose the war to the Greeks, just as Odysseus, in The Odyssey, was fated to return home. Even the gods could not alter these fates, though they could affect how pleasant or unpleasant life was on the way to realizing that fate. Gods also communicated their pleasure or displeasure by manipulating the forces of nature: Thunder was a message from Zeus; earthquakes were the work of Poseidon.