It's pretty easy to prove that God didn't create the universe, given just a couple of very uncontroversial postulates and the definitions of the words "universe" and "God" as most people understand them.
- Define the causal closure of a point in space-time X to be X plus the causal closure of any points that could influence X or be influenced by it.
Define the universe (which we'll also call the "L-universe") as the causal closure of planet Earth as it is today. (If you dislike the use of "planet Earth" or "as it is today" in this proof, you can substitute it for some other subset of the universe that is alleged to be created by God.)
- Postulate that if A created B then A influenced B. This is a pretty trivial postulate - creation of something is obviously a kind of influence over that thing.
- Postulate that creators cannot create themselves. This is also pretty trivial - the concept of creation of an X implies that there is a time before the X exists and a time after which X exists. The creator of X must exist in both of these times, but the creation can only exist in the latter.
Suppose that the universe was created by God.
- This implies that planet Earth was created by God (planet Earth is part of the universe).
- This implies that God influenced planet Earth (creation is a sort of influence).
- This implies that God is in the causal closure of planet Earth (definition of causal closure).
- This implies that God is part of the universe (definition of universe).
- This implies that God could not have created the universe (creators are not part of their creations).
- Which is a contradiction. Therefore, the universe did not have a creator.
This is a formalization of the common "If God created the universe, who created God?" argument but sidesteps the possibility of a creatorless God or a God created by another God by including all such Gods in the larger L-universe.
This suggests that to believe in God, one must have a different definition of "universe" (call it "S-universe") which is a subset of the "L-universe". This brings us to the real value of this proof - any argument for the existence of God that doesn't distinguish between the L-universe and the S-universe must be invalid, because to be true it would have to apply to the S-universe (for which there can be a God) but not to the L-universe (for which we have already seen that there isn't). Some examples of such arguments:
- We don't know how the universe was created, so let's just define God to be whatever created the universe.
- The universe seems well suited to our needs.
- Anything of sufficient complexity must have had an intelligent creator.