The Rational Design project is impressive on its own terms. However, it does not address other approaches relevant to the design of international institutions. To facilitate comparison I survey two “contrast spaces” around it. The first shares the project's central question—What explains institutional design?—but addresses alternative explanations of two types: rival explanations and explanations complementary but deeper in the causal chain. The second contrast begins with a different question: What kind of knowledge is needed to design institutions in the real world? Asking this question reveals epistemological differences between positive social science and institutional design that can be traced to different orientations toward time. Making institutions is about the future and has an intrinsic normative element. Explaining institutions is about the past and does not necessarily have this normative dimension. To avoid “driving with the rearview mirror” we need two additional kinds of knowledge beyond that developed in this volume, knowledge about institutional effectiveness and knowledge about what values to pursue. As such, the problem of institutional design is a fruitful site for developing a broader and more practical conception of social science that integrates normative and positive concerns.