Philosophers have traditionally responded to the question, ‘why does the universe exist?’, in one of two ways. One response is that ‘the universe exists because God created it’ and the other response is that ‘the universe exists for no reason—its existence is a brute fact’. Both these responses are inadequate, since a third response is possible, namely, that the reason the universe exists is that it caused itself to exist. There are at least three ways the universe can cause itself to exist, by (1) a closed, simultaneous causal loop at the first instant of time, (2) beginning with a continuum of instantaneous states in a first half-open second, with each state being caused by earlier states, and (3) being caused to exist by backward causation, where a later event causes the big bang to occur. This suggests that the principle, ‘if the universe begins to exist, it has a cause’ does not support theism (as traditionally has been thought) but instead supports atheism.