The human condition teems with institutions - intertemporal social arrangements that shape human relations in support of particular values - and the social scientific work developed over the last five decades aimed at understanding them is similarly vast and diverse. This book synthesizes scholarship from across the social sciences, with special focus on political science, sociology, economics, and organizational studies. Drawing out institutions' essentially social and temporal qualities and their varying relationships to efficiency and power, the authors identify more underlying similarity in understandings of institutional origins, maintenance, and change than emerges from overviews from within any given disciplinary tradition. Most importantly, Theories of Institutions identifies dozens of avenues for cross-fertilization, the pursuit of which can help keep this broad and inherently diverse field of study vibrant for future generations of scholars.