Idealism, as an approach to International Relations (IR), emerged prominently after World War I, driven by a desire to prevent future conflicts. Its core assumptions are rooted in a belief in human progress and the possibility of creating a more peaceful and just world order. Key assumptions include:

1. Human Nature: Idealists generally believe that human beings are inherently good or at least capable of moral improvement and rational behavior, making cooperation possible.
2. International Cooperation: They contend that international cooperation is not only desirable but achievable through the establishment of international laws, norms, and institutions.
3. Role of Institutions: Idealists place significant faith in international organizations (like the League of Nations or the United Nations) to mediate disputes, enforce international law, and foster collective security.
4. Democracy and Peace: They often assume that democratic states are inherently more peaceful and that the spread of democracy globally would reduce the likelihood of war.
5. Moral Principles: Idealism emphasizes the importance of ethics and morality in foreign policy, advocating for policies based on universal values rather than narrow national interests.
6. Interdependence: They recognize that states are increasingly interdependent, making war a costly and irrational option.

Idealism retains significant relevance in peacebuilding today. Its emphasis on international law and institutions underpins the work of the United Nations, which plays a central role in peacekeeping, conflict resolution, and humanitarian aid. The idealist belief in the power of diplomacy and multilateralism is crucial for addressing complex global challenges like climate change, pandemics, and nuclear proliferation. Furthermore, the focus on human rights and the promotion of democracy, often seen as idealist tenets, are integral to contemporary peacebuilding efforts, aiming to create stable, just, and inclusive societies that are less prone to conflict. While often critiqued for being utopian, idealism provides the normative framework and aspirational goals that continue to guide efforts towards a more peaceful and cooperative international system.