Big Bang Cosmology and Religious Thought

Alexander Friedmann and Georges Lema\^itre are undoubtedly the real fathers of Big Bang cosmologies. In this article I study the influences their work underwent due to some religious as well as anti-religious ideas. During his career Lema\^itre faced criticisms coming from non-believing scientists, who reproached him (wrongly) to have developed his primeval atom cosmology for conciliatory reasons. In the former case of Friedmann, we know that his 1922 proposal of a "creation of the world out of nothing" was criticized by Einstein for metaphysical reasons. The essence of such hostile reactions is the fact that presumably "good" scientific contents should not be influenced by religious ideas. Nevertheless, metaphysical and theological ideas can play an important role inside the science research processes, as an epistemological tool helping to clarify the use of some fundamental notions.