L'Être et le Néant
"Being and Nothingness" is considered Sartre's most important philosophical work, and the most important non-fiction expression of his existentialism. Christian existentialist Gabriel Marcel wrote that it was of "incontestable" importance and ranked among the most important contributions made to general philosophy. While Marcel noted the influence of Heidegger on "the form at least" of "Being and Nothingness", he also observed that Sartre diverged from the views expressed by Heidegger in "Being and Time" (1927) in important ways, and that Sartre's contributions were original. Marcel considered Sartre's analysis of bad faith "one of the most outstanding and solid" parts of "Being and Nothingness", writing that it prevented Sartre's arguments from being purely abstract. Marcel saw one of the most important merits of the work to be to show "that a form of metaphysics which denies or refuses grace inevitably ends by setting up in front of us the image of an atrophied and contradictory world where the better part of ourselves is finally unable to recognise itself."