Does neorealism contain a conception of human nature? Although neorealists usually claim to sidestep the question of human nature altogether, scholars frequently trace the theory back to the work of Thomas Hobbes, a philosopher who in fact defended a robust account of human motivations. As a result, some scholars have concluded that neorealism contains a Hobbesian view of human nature. Against the conventional wisdom, this article argues that neorealism contains a Rousseauian philosophical anthropology. Whereas Hobbes provides a deeply pessimistic account of human motivations, Rousseau combines optimism about human motivations with pessimism about social structures. Rousseau’s critique of Hobbes profoundly influenced neorealism’s founding father, Kenneth Waltz, a political theorist who later gravitated towards International Relations. After exploring Waltz’s reading of Rousseau and demonstrating Rousseau’s influence on Waltz’s theory, the article investigates what is gained by reading neorealism as Rousseauian. Returning to the Rousseauian roots of neorealism reveals the true character of the tragic heuristic employed in neorealist theory, sheds new light on the role of pity in neorealist foreign policy, and clarifies the logic of the theory itself.

This article examines how the principles of complex systems can illuminate recurring mechanisms of change in theories of international relations. It applies the logic of complex systems to two specific puzzles in international politics – the problem of theorizing change in structural realism, and the dynamics of cross-border democratic diffusion. In the first case, by shifting the analysis of anarchy's consequences from state behavior to state attributes, complex systems can illustrate the sources of domestic and international transformations embedded in structural theories. This approach offers a way to think about democratization as a global process of interstate competition and socialization driven by the pressures of anarchy. In the second case, the principles of co-adaptation in complex systems can help reframe diffusion not as the unilinear spread of democracy but as the interplay of self-reinforcing and self-dampening dynamics, whose interaction shapes both actor expectations and democratic outcomes. In both cases, complex systems serve a limited but useful role; although not conducive to theory creation, the approach provides a useful analytical prism for examining patterns of change and continuity in global processes, and highlights concrete ways of improving models of transformations in international politics.