Who created God?
When theists ask "Who created the universe? It must have been God", asking "Who created God?" is a way of turning the original question back on itself. This is the most concise answer to the first-cause argument.
Asking about God's creator is a way of drawing attention to the fact that inventing a god is not an explanation for the existence of the universe, or of unexplained features within the universe. On the contrary, it fails as an explanation because it does nothing more than push the question of origin up a level, and on this new level the same problem exists.
In a more general way, this is a template for the technique of turning theistic questions about the world around on the God that they use to explain it. It can also be used as a response to arguments such as:
- The natural-law argument ("If the order of natural laws can only be explained by a creator, then what explains the order of the creator?")
- Irreducible complexity ("If complexity can only be explained by an intelligent designer, then how do you explain the complexity of the designer?")
- Morality, as in the Euthyphro dilemma ("If God is needed to tell us what is right and wrong, then on what basis does God decide what is right and wrong?")
A common theistic response is that God is specially exempt from the rules they have invented, because he exists "outside of time" and so is not subject to rules such as "everything requires a creator." (See also Kalam.)
This argument is ultimately self-defeating. If there exist things which are not subject to the rules, then the rules are not really rules, but more like guidelines. If theists grant that some things do not need a creator, then we may as well simplify and say that it is the universe, or some other ungodlike entity, that requires no creator.
Of course, the theistic counter to this is that God is special. This is petitio principii, since it is the specialness of God that is what they are trying to prove.