“To help us think about this question, it is useful to start by considering a slightly different question. Rather than think about the origin of natural reality, let us consider the origin of causal reality. Since causal reality is the whole causal network, it cannot be that there is a cause of causal reality: such a cause both would and would not belong to causal reality. So it cannot be that it is true both that causal reality began to exist and that whatever began to exist had a cause of its beginning to exist. In order to maintain logical consistency, theists and atheists alike must either accept that causal reality did not begin to exist, or else accept that there are some things that began to exist that do not have causes of their beginning to exist.”