Pius XII condemned atheism's “most ignoble corruptions” in his 1956 encyclical Haurietis Aquas, along with its “lethal tenets” in 1958's Meminisse Iuvat. Only six years later, however, in 1964, Vatican II's Lumen Gentium affirmed the possibility of salvation for “those who, without any fault of theirs, have not yet arrived at an explicit knowledge of God” (article 16). Furthermore, the following year's Gaudium et Spes 19–21, drafted by Paul VI's newly-founded Secretariat for Non-believers, offers, among much else, a sympathetic overview of contemporary atheisms, and invites their contemporary adherents to “a dialogue that is sincere and prudent”. These paragraphs, according to Ratzinger, “may be counted among the most important pronouncements of Vatican II”.

Evidently, comparing Pius XII's “lethal tenets” to Vatican II's salvific optimism, profound developments are manifest in the Catholic engagement with atheism. Primarily responsible for this are, I argue, two episodes in French Catholic history in the decades preceding Vatican II: a) the unprecedented dialogue of Catholic intellectuals with modern atheism, following the French Communist Party's main tendue (“outstretched hand”) during the period of the Popular Front (1934–38); and b) the ‘priest-worker’ experiment, initiated by Henri Godin and Yvan Daniel's 1943 publication of La France – Pays de Mission?