Classical realism is an international relations theory from the realist school of thought. Realism makes the following assumptions: states are the main actors in the international relations system, there is no supranational international authority, states act in their own self-interest, and states want power for self-preservation. Classical realism differs from other forms of realism in that it places specific emphasis on human nature and domestic politics as the key factor in explaining state behavior and the causes of inter-state conflict. Classical realist theory adopts a pessimistic view of human nature and argues that humans are not inherently benevolent but instead they are self-interested and act out of fear or aggression. Furthermore, it emphasizes that this human nature is reflected by states in international politics due to international anarchy.

Thomas Hobbes was an English philosopher. Hobbes is best known for his 1651 book Leviathan, in which he expounds an influential formulation of social contract theory. He is considered to be one of the founders of modern political philosophy.