The term scientism is used in several ways. It is used to denote an epistemological thesis according to which science is the source of our knowledge about the world and ourselves. Relatedly, it is used to denote a methodological thesis according to which the methods of science are superior to the methods of non-scientific fields or areas of inquiry, or even used to put forward a metaphysical thesis that what exists is what science says exists. In recent decades, the term scientism has acquired a derogatory meaning when it is used in defense of non-scientific ways of knowing. In particular, some philosophers level the charge of “scientism” against those (mostly scientists) who are dismissive of philosophy. Other philosophers, however, embrace scientism, or some variant thereof, and object to the pejorative use of the term scientism. This book critically examines the arguments for and against scientism, of various productive kinds to answer the central question: does scientism pose an existential threat to philosophy, or should philosophy become more scientific?