The combination of multiple theories in policy studies has a great potential value—new combinations of theories or concepts may produce new perspectives and new research agendas. However, it also raises important ontological, epistemological, methodological, and practical issues that need to be addressed to ensure disciplinary advance. This article identifies three main approaches: synthesis, in which we produce one theory based on the insights of multiple theories; complementary, in which we use different theories to produce a range of insights or explanations; and contradictory, in which we compare the insights of theories before choosing one over the other. It examines the issues that arise when we adopt each approach. First, it considers our ability to “synthesize” theories when they arise from different intellectual traditions and attach different meanings to key terms. Second, it considers the practical limits to using multiple theories and pursuing different research agendas when academic resources are limited. Third, it considers the idea of a “shoot-out” in which one theory is chosen over another because it appears to produce the best results or most scientific approach. It examines the problems we face when producing scientific criteria and highlights the extent to which our choice of theory is influenced by our empirical narrative. The article argues that the insistence on a rigid universal scientific standard may harm rather than help scientific collaboration and progress.