If you are a six-year-old child without much theological training you can be excused for asking the question, “What caused God?” If you are not, then never, ever ask that question in public—it only makes you look like a philosophical ignoramus. Philosopher Edward Feser explains why, and clears up several other misunderstandings about the cosmological argument:
Most people who comment on the cosmological argument demonstrably do not know what they are talking about. This includes all the prominent New Atheist writers. It very definitely includes most of the people who hang out in Jerry Coyne’s comboxes. It also includes most scientists. And it even includes many theologians and philosophers, or at least those who have not devoted much study to the issue. This may sound arrogant, but it is not. You might think I am saying “I, Edward Feser, have special knowledge about this subject that has somehow eluded everyone else.” But that is NOT what I am saying. The point has nothing to do with me. What I am saying is pretty much common knowledge among professional philosophers of religion (including atheist philosophers of religion), who – naturally, given the subject matter of their particular philosophical sub-discipline – are the people who know more about the cosmological argument than anyone else does.
In particular, I think that the vast majority of philosophers who have studied the argument in any depth – and again, that includes atheists as well as theists, though it does not include most philosophers outside the sub-discipline of philosophy of religion – would agree with the points I am about to make, or with most of them anyway.