Wow, what a tangle of verbosity. Yes, you could be a brain in a vat. Or you could be a brain on a biped. Obviously you cannot distinguish between these two possibilities merely by <i>thinking</i> about them, because your thought processes are equally compatible with either scenario (by construct, by the premise of the question). A simulation good enough to be indistinguishable from reality, cannot be distinguished from reality -- that's the definition.<p>The fun thing about this quack philosophy is that's it's falsifiable, that in a couple decades, we'll actually have brains in vats, and kids will play games where they shuffle a kid's brain around and have him guess if he's in a vat or not. And with the higher-end iVats, they'll never be able to tell. And they'll totally <i>ridicule</i> the tenured philosophy faculty, they'll be so mean, what the hell have you been doing with your grant money?