The insights of social psychology are not thoroughly integrated into international relations theory, yet social psychology has much to offer. Social psychology provides a conceptualization of a number of varieties of trust – moralistic, strategic, and generalized – and their opposites that implicitly drive the logic of major works of international relations. It also reveals the empirical presence of a number of different types of trusters who make different assumptions about the trustworthiness of others and consequently show markedly different propensities towards cooperation. The rough correspondence between these different ‘social orientations’ and the logics of the three approaches of structural realism, neoliberal institutionalism, and constructivism suggest that individuals carry a crude paradigm in their minds. Metatheoretically, the implication for international relations theory is that scholars capture a part but not the totality of world politics, the behavior of those who trust (or do not trust) in a particular way that matches the logic of their paradigms. Theoretically it suggests a research agenda at multiple levels of analysis, utilizing all of the types of trust and trusters. I review the work of others that offers some preliminary evidence for its plausibility, suggest some hypotheses of my own, and address potential theoretical objections.