Atheism is just the last step of an abstraction and sublimation process of religions towards rationality. This is a simplifcation, but it goes approximately like this: we started praying to animals, then natural phenomena, then totems, half-human half-animal polistheistic gods, human politheistic gods, then a monotheism whose god was a very human-like tyrant (judaism), then deism, the abstract god justified with rational arguments, and finally atheism. Atheism as a proposition, i.e, god does not exist, looks as a taxative negation of all the previous phases, but as a generalised historical phenomenon it is not a negation but a culmination. Read Hegel, though I don't agree with much of what he postulated.