Juan Comesana pointed me to “this discussion”:http://digg.com/science/Are_you_Living_in_a_Computer_Simulation__2 of Nick Bostrom’s “Simulation Argument”:http://www.simulation-argument.com/matrix.html at “digg.com”:http://digg.com/. I haven’t read through all of the comments, and I think Zeno’s paradox would prevent reading _all_ of them in any case. But they don’t seem to have got to “my reply”:http://brian.weatherson.org/sims.pdf, and I wouldn’t be a real blogger if I didn’t take this opportunity for self-promotion.

It’s been a while since I wrote it, but I think my reply holds up OK. If I was doing it now I’d make much more of the evidential internalism assumption in Bostrom’s argument. It is very intuitive at first that we have the same evidence as a BIV. I guess if it wasn’t I guess these sceptical arguments wouldn’t have the pull they actually do. But I don’t think that a purely phenomenal account of evidence actually has much to be said for it on reflection. It seems to be constitutive of the notion of evidence that evidence is a guide to the truth. So even if _our_ evidence is constituted by our phenomenal states (which I doubt), we shouldn’t think that a BIV’s evidence is constituted by _its_ phenomenal states, because its phenomenal states don’t give it any information about how the world is. So we don’t have the same evidence as a BIV, so nothing about its doxastic/epistemic state is relevant to our doxastic/epistemic state. And that’s even ignoring the worries about indifference that I set out (at interminable length) in “that paper”:http://brian.weatherson.org/sims.pdf and in “the paper on Elga’s indifference principle”:http://brian.weatherson.org/evil.pdf.