Why do you not believe in God?

[ktulu]

But where's the question begging? The KCA doesn't say "Everything begins to exist except for this one thing." It says:

1) Everything that begins to exist has a cause.
2) The universe began to exist
3) Therefore, the universe had a cause.

It doesn't assume that the universe had a cause. Since that's the only conclusion here, it can't possibly be begging the question.

Ok, let's try this one more time

I think we both agree that if you imply the conclusion in the premise the argument is question begging.
If you want to get around the question begging, your argument would have to be something like this:
1. Everything has a cause
2. The universe
c. The universe has a cause.

Obviously not sound. So what KCA is attempting to do, is tie the first two premises with beginning to exist. The issue is, when you introduce the "begin to exist" condition, you automatically imply that some things DO NOT begin to exist. Hence the question begging, because you are attempting to prove that some cause, which does not begin to exist, is THE CAUSE, or god, or whatever else your argument is trying to prove.