This article argues that the fragmentation of International Relations (IR) theory is not only a problem of competing schools, but a deeper ontological dispute over social totality. Realism, liberal institutionalism, constructivism, critical theory, post-structuralism, Global IR, and decolonial approaches each assume a different image of world order and of the human subject. Through conceptual genealogy and critical reconstruction, the article revisits Kant, Hegel, Marx, Lukács, Dussel, Quijano, Mariátegui, Zavaleta Mercado, Wynter, Said, Glissant, Wallerstein, and postcolonial IR. It proposes heterogeneous relational totality as a way beyond both closed systemic determinism and pure fragmentation. This framework rethinks power, agency, temporality, recognition, and emancipation through coloniality, planetary interdependence, and relational human existence.