The definition of human nature plays a very important role in Thucydides" account of the Peloponnesian War. The investigation of this concept is basic and complex, subjective and objective, and is undertaken by the author in terms of the rise of democracy and the individual's intrinsic need for power. According to Thucydides, both of these conflicting ideas stem from this idea of human nature, namely, the inherent goal of the human being is to follow self interest. .
According to Thucydides, history repeats itself because of human nature. He states that there are "events which happened in the past and which (human nature being what it is) will, at some time or other and in much the same ways, be repeated in the future" (I.22), emphasizing the basic yet ongoing battle of forces within the human psyche. From a philosophical perspective, there is a causal relationship between events in history and the inherent need for survival punctuated by this bleak theory of our nature. In other words, once the acquisition of basic utilities for survival is met (clothing, shelter, food, etc), the symptom may be temporarily alleviated but the cause remains, resulting in the continuing human drive to insure safety and security by any means possible. Most importantly this need may result in war, which is the fight for power, yet at its roots war is just another way to insure ones safety and security from outside forces. Over and over wars are fought for various reasons, but at the core there is only one explanation for this atrocious act, and as I would say it is just a manifestation of insecurity. Thucydides" insight into the role of human nature and history is very unique, and though my account is simplistic, the philosophy and logic of this view is evidence for his genius as a historian. .