This book is the first detailed and focused defense of necessitarianism. The author’s original account of necessitarianism encourages a reexamination of commonly held metaphysical positions as well as important issues in other, related areas of philosophy. Necessitarianism is the view that absolutely nothing about the world could have been otherwise in any way, whatsoever. Most philosophers believe that necessitarianism is just plain false and presume that some things could have been otherwise than what they are. In this book, the author argues that necessitarianism is true and the view that some things in the world are contingent—what the author terms contingentarianism—is false. The author assesses various theories of contingency, including the possible worlds theory, combinatorialism, and dispositionalism, and argues that no theory can successfully explain why an entity is such as it is rather than not. She then lays out a case for necessitarianism and provides responses to various objections. The book concludes with an explanation of the ways in which necessitarianism is relevant to issues in ethics, philosophy of mind, and social philosophy. A Case for Necessitarianism will be of interest to scholars and advanced students working in metaphysics, logic, and philosophy of science.