Imagination was central to Sartre’s philosophical work throughout his career. It had been the topic of his dissertation submitted for the diplôme d’études supérieure degree in 1927. His first book was a critical analysis of philosophical and psychological theories of imagination since Descartes, published in 1936. He followed this up four years later with a book that remains one of the most thorough and sophisticated analyses of imagination in Western philosophy. This “phenomenological psychology” of imagination is fundamental to the theory of human existence he published three years later in Being and Nothingness, to the rethinking of this theory across Saint Genet published nine years after that, and to the monumental attempt to integrate and refine his total philosophical outlook in The Family Idiot published toward the end of his life.