Jean-Paul Sartre is one of the most famous philosophers of recent times; he is also one of the most difficult. His fame owes much to his political and emotional engagements, as well as to the wealth of ideas expressed in his novels, plays, journals and critical essays. The difficulties arise as soon as we ask about the reasons for endorsing those ideas. In order to achieve a proper understanding of his views, and the reasons that might support them, we need to look at that part of Sartre's work where he explicitly addresses their content, presuppositions and implications; in other words, we need to explore his philosophy.

The philosophical writings of Sartre span fifty years. During that period, Sartre articulated, developed and elaborated, in sometimes unpredictable ways, a number of seminal arguments on major topics of philosophical enquiry. The desire for securing a reliable compass through the sea of Sartrean volumes, diaries and still unpublished manuscripts might make one adopt a sideways approach to Sartre's philosophy. We might wish to introduce his philosophy by categorizing his work under fixed headings, such as “existentialism”, “socialism” or “phenomenology”. This is a justifiable way to proceed if we already know what those terms mean, and how they should apply to each Sartrean text that is taken to express those schools of thought. Another approach may introduce Sartre's trajectory as filling the intellectual gap between, say, certain Austrian and German philosophers, on the one hand, and certain French or American philosophers, on the other.