This book attempts to demonstrate how Jean-Paul Sartre manages to solve two serious problems within the history of existentialism as a movement of thought. The first problem is that of the social dimension of existentialism that is, the question of how it is possible to perceive existentialism as the search for a common freedom. The second, being the consequence of the first, is that of the relevance of the search for social and political freedom from an existentialist point of view.