In the Melian Dialogue, the Athenians tell the Melians that “the strong do what they have the power to do, and the weak accept what they have to accept.” What does this tell us about the Athenians, who prided themselves on their democracy and sense of fairness?
This statement is one of the classic statements of realism in the field of international relations. What it tells us about the Athenians is that they were realists in terms of their international relations, regardless of what their domestic political system was like. This fits with what realism predicts.
Realism holds that all states, regardless of the type of domestic government they have, will seek to maximize their own power and security. States cannot afford to be sentimental or fair in their dealings with one another. Instead, they must simply do whatever is in their interests when those interests are defined in terms of power and security.
So, what this tells us about the Athenians is that they were acting just as realism predicts. They could hold idealistic values that they applied to domestic politics, but in international relations, they acted out of self-interest.