Descartes’s meditator thinks that if she does not know the existence of God, she cannot be fully certain of anything. This statement seems to contradict the cogito, according to which the existence of I is indubitable and therefore certain. Cannot an atheist be certain that he exists? Atheistic knowledge has been discussed almost exclusively in relation to mathematics, and the more interesting question of the atheist’s certainty of his existence has not received the attention it deserves. By examining the question (...) of atheistic knowledge in relation to the cogito, I articulate the advantage Descartes sees in having knowledge of God. I challenge a long-held reading of the cogito where “I exist” is the first full certainty and argue that while atheistic cogito is more certain than atheistic knowledge in mathematics, it cannot be a starting point for lasting and stable science, because science requires knowing the existence of the non-deceiving God. (shrink)