Pierre Hadot is arguably one of the most influential and wide-ranging historians of ancient philosophy writing today. As well as having an important influence on the work of Michel Foucault, Hadot's work has been pivotal in the development of contemporary French philosophy. His work is currently concerned with a redefinition of modern philosophy through a study of ancient life and ancient philosophical texts. This book presents a history of spiritual exercises from Socrates to early Christianity, an account of their decline in modern philosophy, and a discussion of the different conceptions of philosophy that have accompanied the trajectory and fate of the theory and practice of spiritual exercises. Hadot's book demonstrates the extent to which philosophy has been, and still is, above all else a way of seeing and of being in the world.