Objective/Context:

This article aims to explain the causes of the virtual disintegration of the Union of South American Nations (UNASUR) from the perspective of analytical eclecticism. It is part of the growing literature around the debate on the end of International Relations theory in which analytical eclecticism and integrative pluralism emerge as viable but contested explanatory strategies.

Methodology:

Based on recent historical evidence and a voluminous body of research on the object of study, we start from analytical eclecticism and sequentially analyze UNASUR from neoclassical realism, institutional liberalism, and social constructivism to comprehensively explain the case.

Conclusions:

While any of our three approaches can convincingly explain the reasons for UNASUR’s failure, none of them by itself captures the full complexity of its demise. The explanations provided by these analytical approaches are not contradictory but complementary. The creative combination of different International Relations approaches enhances our understanding of an atypical case in the history of Latin American regionalism, generally characterized by the resilience of regional organizations. The analysis of the disintegration of UNASUR reveals structural challenges and tension factors for South American regionalism. It helps understand why PROSUR, as the supposed successor to UNASUR, has not yet taken off.

Originality:

Research on UNASUR and its destiny has been prolific. Rival explanations such as neoclassical realism, institutional liberalism, and social constructivism have prevailed. This article is the first to collect and integrate these explanations to provide a comprehensive response that accounts for the complex process of South American disintegration.