As is typical of philosophers promoting metaphysical hunches, Adams and Aizawa (2001) explicitly associate the internalist view with "common sense,"I'm probably as much against "metaphysical hunches" as are 70% of philosophers, but I don't think that "common sense" must only be a reflection of prejudice, thoughtlessness, or metaphysical hunches. I think the idea that mental or cognitive processes take place in the brain is supported by certain relatively informal experiences with injuries in battle. (I've posted a sketchy speculative description of his idea here.) It's a kind of defeasible empirical conjecture (that I happen to think is also reinforced by more rigorous scientific work) and not a mere metaphysical hunch. The conjecture could be false, but it would still be a false a posteriori, empirical conjecture.