Liberalism and Constructivism

Liberal international relations theory traces its philosophical roots to Immanuel Kant's 1795 essay Perpetual Peace: A Philosophical Sketch, which proposed that lasting peace among states could be built on three definitive articles: republican constitutions, a pacific federation of free states, and a cosmopolitan right of hospitality enabling commerce and interaction among peoples. Kant argued that republics, because their citizens bear the costs of war and must consent to it, would be less inclined to fight one another than autocracies, whose rulers could wage war without bearing its burdens directly. This argument, developed nearly two centuries before the term existed, is widely regarded as the philosophical ancestor of the democratic peace thesis, and Kant's broader vision of an expanding zone of peace among like-minded, commercially interdependent republics anticipated much of twentieth-century liberal IR theory.