The theme of the inevitability of a war between Athens and Sparta runs through Thucydides book I, which makes the reader focus not on 'responsibility' but on 'nature' and its irreversible dynamic. It not only shows that war between the Athenians and the Spartans was unavoidable and that no poleis or individuals should be held responsible for it, but also describes the steps by which the two sides became gradually aware that war was unavoidable. Thucydides discloses the processes that made the imminence of war a certainty in the mind of both the Athenians and the Spartans in 433-432 BC; such awareness worked on a psychological level, predetermining war before it broke out.
