It's similar, in that I'm arguing we can't prove it doesn't exist and is perhaps self-evident. Obviously, no one here is going around "believing in things" simply because we can't prove them wrong. So whether or not this is a sound argument hinges on whether or not you think free will is self-evident.

I am not sure of that, myself, and I'm not convinced the answer is known to anyone. I don't think physics really answers that question. Neither does psychology or neuroscience.