kjs

A brain transplant is the only transplant operation where it's better to be the donor rather than the recipient.

The suggestion that we may be in a matrix (or brain-in-a-vat) may indeed be arbitrary. But I don't think the idea that somebody could be put into a matrix is not. The evidence for this fact come mostly from the Science channel (SCI): 1) Ocular implants - bypass the defective ear and stimulate nerves to correspond to sounds recived by a microphone. 2) Restoring vision to the blind - again, byass the defective eye and stimulate the optical nerve with visual signals from a video camera 3) Computers with amazing 3d simulations and virtual worlds (mostly from the realm of movies and computer games) So, given a century or two, this brain-in-a-vat capability may very well be an actuality. (Of course, ethically I highly doubt it will be actualized). This alters the orginal posters query, from an arbitrary claim about our existence to something that at least has the cognitive status of the possible. To me the interesting question is this: Could such person in a matrix, in principle, ever come to know that they are in the matrix and gain access to the "real" reality which we inhabit? And if not, how to reconcile this with the Objectivist belief that no aspect of reality is beyond mans capacity to discover. As an aside, I can think of an trivial version of a "brain-in-a-vat" that is possible today. Just raise an infant in a sensory deprivation chamber (highly immoral, duh). It would be ridiculous to claim that such a person would be able to get outside of its vat and discover the rest of world.