  International relations realists emphasize the constraints imposed on politics by the nature of human beings, whom they consider egoistic, and by the absence of international government. Together these factors contribute to a conflict-based paradigm of international relations, in which the key actors are states, in which power and security become the main issues, and in which there is little place for morality. The set of premises concerning state actors, egoism, anarchy, power, security, and morality that define the realist tradition are all present in Thucydides.