How does realism differ from idealism in international relations?

In the study of international relations, realism and idealism represent fundamentally different perspectives on how states behave and how the global system functions.

Realism

Realism emphasizes the role of the state, national interest, and power in an anarchic international system. Realists argue that because there is no centralized global authority, states must rely on their own capabilities to ensure survival. They are generally pessimistic about the potential for radical systemic reform, viewing human nature as inherently inclined toward competition and conflict. Realists believe that policy makers should prioritize core national interests—such as territorial integrity and economic stability—over ideological or moral crusades, which they argue can destabilize the international order.12

Idealism

Idealism, which realists often critique as being deluded or overly optimistic, holds that international policy should be guided by moral and legal principles. Idealists emphasize the possibility of progress through the construction of international institutions and the promotion of universal cooperation. While realism focuses on the struggle for power as the essence of politics, idealism advocates for adherence to ethical standards and the pursuit of collective security to mitigate the risks of war.12