Turing machines are deterministic, brain might not be because of quantum mechanics happening. Of course there is no proof that this is related to creativity.
If the brain exceeds the Turing computable, then all bets are off, but we have no evidence to suggest it does, nor that doing so is possible. This was in fact my original argument.
The only viable counter to my argument is demonstrating that there are computable functions outside the Turing computable, and that humans can compute them.