History of the Peloponnesian War

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. While Thucydides accounts for oracles, myths, gods, and soothsayers, his purpose is to show how believing in them can impact human decision-making. Oracles, myths, and soothsayers have the power to affect outcomes because people believe them, not because they themselves dictate outcomes.

In Book 1, for example, as the Spartan’s sought to establish a pretext for war, Thucydides notes that they consulted the oracle at Delphi “to inquire from the god [Apollo, the god of prophecy] whether it would be wise for them to go to war” (103). According to the Spartans’ interpretation, the oracle indicates that they might win if they fight “with all their might” and that the god “would be on their side” (103). The oracle’s response, as the Spartans translate it, justifies optimism, but it is ambiguous enough that they seek a second meeting with their allies to ensure they have full agreement on a declaration of war against Athens. Because the Spartans interpreted the oracle somewhat ambiguously, they took extra measures to ensure all of their allies were in agreement, which may ultimately have benefited them in the war. Thus, outcomes are not decided by the gods, but by human actions and reactions.

In the above example, Thucydides alludes to the mutability of oracular meanings. In Book 2, he states it outwardly when discussing the plague and its impact on the war. Thucydides notes that oracles could be interpreted according to the wishes of the interpreters. When the plague hits Athens, residents turn to oracles to help them understand why such terrible things are happening to them. They fixate on an old oracle that said, “War with the Dorians comes, and a death will come at the same time” (156, italics in original). Thucydides points out that there had been a dispute about the word “death,” with some arguing the word in the oracle was actually “dearth” (156). Since so many people were dying, they decided the word must indeed have been “death,” but Thucydides believes "it was a case of people adapting their memories to suit their sufferings” (156). He adds that “in all probability people will quote the other version,” in the event of a further war against the Dorians, in which “a dearth results” (156).

Thucydides instead seeks causal patterns in empirical facts he has observed or heard from multiple eyewitnesses, whether these concern nature, chance, and/or human motivation and action.

Nature repeatedly plays a decisive role in the actions people take during the war but not because these actions are divinely ordained. The natural world has its own causal chain. The most obvious empirical instance is the cycle of the seasons, which Thucydides uses to mark the passage of years. Another significant instance is his meticulous description of a tsunami in Book 3. Thucydides notices that a “huge wave” follows a series of earthquakes. The earthquake’s full force draws the sea “away from the shore and then suddenly sweeps [it] back again even more violently,” washing away a city and causing lasting flooding (247). Thucydides deduces that these two events—the earthquakes and the wave—are connected. It logically follows that if earthquakes and waves are causally linked, further natural causes, as yet unseen, may exist to explain earthquakes. 

Causal chains in nature, then, are indifferent to human endeavors, rather than being commentaries on them. In Book 2, the city of Plataea is almost destroyed by fires the Spartans set, but a thunderstorm and heavy rains “saved the situation” (173). In Book 3, Plataeans plotting a breakout from their besieged city wait for a stormy night to mask any noise they make. The “violent” storm then aids their escape (206). Several times in the text, negotiations stall or end prematurely due to earthquakes. These storms and earthquakes had causes neither affected nor invited by the gods’ manipulation.

Human actions can also lead to chance outcomes as when, in Book 6, the Athenians seek alliances in Sicily. They request an alliance from the city of Catana. The Cataneans agree to speak with the generals only. The rest of the army is told to wait outside the city’s walls. A group of soldiers enters the city anyway by “breaking down a badly built gate in the walls” (442). Catana’s pro-Syracusean party sees the Athenian soldiers strolling through the city, assumes the city has established an alliance with Athens, and flees the city. As only pro-Athenians are left behind, the vote to form an alliance with Athens indeed passes.

Thucydides also repeatedly shows how human motives and actions can affect critical outcomes. One of the text’s more famous examples occurs after the Mytilenian debate, in Book 3. The Athenian assembly convenes to discuss how to punish Mytilene for attempting to revolt. Creon argues for putting the island’s entire male population to death, including those who did not take part in, or even actively resisted, the revolt. He believes mercy will be seen as weakness since “it is a general rule of human nature that people despise those who treat them well and look up to those who make no concessions” (215).

The motion to slaughter the entire population passes, and a ship is sent to Mytilene to carry out the execution order. After the ship has sailed, the Athenians rethink their decision and reconvene the assembly. Cleon repeats his argument, but a second speaker, Diodotus, argues passionately for showing mercy to the innocent. His argument sways the assembly, and a second ship is sent to intercept the first, which has a twenty-four-hour head start. Thucydides explains that Mytilenian ambassadors aboard the second ship “promised great rewards if they arrived in time” (223). The second ship arrives just in time to prevent the massacre. Human motivation, both internal and external, saves the Mytilenians. The crew on the second ship was more motivated to row quickly and arrive at their destination than the crew on the first, as the second crew’s cause was just, and they were promised material rewards.

Human motivations and actions can also be influenced by human flaws—arrogance, fear, or simple human error—and have unexpected outcomes. In Book 6, the Athenians debate in their assembly whether to send an expedition to conquer Sicily. Alicibiades argues in favor, telling the Athenians it is the surest way to secure and expand their influence and territory, the very mistake Pericles warned against at the start of the war. To the objection that leaving for Sicily will leave Athens vulnerable at home, Alcibiades counters that Athens' unparalleled navy will keep the home front safe. Nicias argues against the expedition by emphasizing how many people and resources will be needed to ensure success. However, instead of putting off the Athenians, Nicias’ argument further mobilizes them as old and young look forward to the challenge and activity such an undertaking would involve. Thucydides notes, “just the opposite of what Nicias had imagined took place” (425). In this way, Thucydides emphasizes the limits of human perception and the impossibility of accurately seeing into the future (the province of prophecy). Further damaging for the Athenians, “the few who actually were opposed to the expedition were afraid of being thought unpatriotic if they voted against it, and thus kept quiet,” which fueled the expedition’s launching (425). The entire expedition was annihilated in 413, leading to catastrophic loss of resources and troops and ultimately to the Athenians losing the war. Pericles’ fear that Athens’ mistakes would be the city’s undoing is realized due to the arrogance and errors of its people, not the will of the gods.