Even the early publications of J.-P. Sartre, such as 'L'Etre et le Néant' and 'L'existentialism est un humanism' have not been always received as unequivocally atheist. Etienne Gilson, for instance, found some aspects of Sartre's atheistic opinions rather shifting and tentative. Sartre himself addressed his disbelief in God in his autobiography (cf. 'Les Mots', 1964) and in a long discussion with Simon de Beauvoir, which they held through the summer and fall of 1974. In these documents he expressed his personal conviction that God did not exist, but at the same time he added that atheism was not a simple position to be either upheld or rejected but rather a 'long term and painful enterprise'. In 'Les Mots', he mused that in his case that enterprise was successfully brought to an end, but when talked with de Beauvoir, he quizzically claimed that his materialistic atheism still contained some divine elements in it. To be sure, however, he unswervingly believed throughout his life that an acceptance of God was incompatible with making full use of man's freedom. And yet, at the end of his life, in a conversation with Benny Lévy that was published in March 1980, a few weeks before his death, Sartre declared that human morality could best be built by accepting a vision of God along the lines laid down by Judaism. Taking all these fact into account, the author claims that both in the life of J.-P. Sartre, and in his philosophy, atheism was not a thoroughly consistent and convincing position.