If, Skeptic, you "accept that causation is a universal", are you not, in the last analysis, equating everything, even humanity, with machinery? If my behaviour is the result of causal chains, how can I accept praise for helping an old lady across the street, or be blamed for stealing the contents of a blind man's begging bowl? Both are the result only of my genes and environment.

And if causation applies also to my thoughts, then I'm only thinking what I think now because of my past experiences, including that time a fly farted on my head when I was three. So I have no reason to think that my thoughts bear any correspondence to reality: they're not necessarily true, they're just caused (why should the two coincide?). And if they're not true, I have no reason to believe that causation is a universal. But equally, reason is invalidated.