Psy-Kosh - "Well... the computation your brain is, under the hood, performing when you're trying to figure out things about "what should I do?""

That just pushes my question back a step. Don't the physical facts underdetermine what computation ('abstracted idealized dynamic') my brain might be interpreted as performing? It all depends how you abstract and idealize it, after all. Unless, that is, we think there's some brute (irreducible) facts about which are the right idealizations...