Bostrom's Response to My Discussion of the Simulation Argument
A few days ago I posted a discussion of Nick Bostrom's Simulation Argument, which aims to show that there is a substantial chance -- perhaps about one in three -- that we are living in a computer simulation. I raised three concerns about the argument but ultimately concluded that although simulationism is crazy (in my technical sense of "crazy"), it's a cosmological possibility I don't feel I can dismiss.
Bostrom and I had an email exchange about that post, and he has agreed to let me share it on the blog.
So, first, you'll want to read my discussion, if you haven't already, and maybe also Bostrom's article (though I hope the summary in my discussion does justice enough to the main idea for the casual reader).
Bostrom's Reply:
Dear Eric,
Thanks for your thoughtful comments and for posting on your blog.
A few brief remarks. Regarding (A) and deriving an objection from externalism: There are a few things said in the original paper about this (admittedly quickly). For example, what do you think of the point that if we consider a case where we knew that 100% of everybody with our observations are in sims, we could logically deduce that we are in sims; and therefore if we consider a series of cases in which the fraction gradually approaches one, 90%, 98%, 99%, 99.9%, … , it is plausible that our credence should similarly gradually approach one? (There is also the whole area of observation selection theory, which uses stronger principles from which the “bland indifference principle” needed for the simulation argument drops out as an almost trivial special case.)
Regarding (B), I think it’s a somewhat open question how many conscious fellow traveler the average simulated conscious being has. Note that there need be only a few ancestor simulations (big ones with billions of people) to make up for billions of “me-simulations” (simulations with only one conscious person). Another issue is whether it would be feasible to create realistic replicas of human beings without simulating them in enough detail that they are conscious - if not, we have observational evidence against the me-sim hypothesis.
Regarding possible interaction between (B) and (C): no. 4 in http://www.simulation-argument.com/faq.html might be relevant?
With best wishes,
Nick
My Follow-Up:
Dear Nick,
Thanks for the thoughtful reply! ...
[Regarding the response to A] I don’t accept the slippery slope. As long as there is one non-sim, that person’s grounds for believing she is a non-sim might be substantially different than the grounds of all simulated persons no matter how many sims there are, especially if we accept an externalist epistemology. Compare the Napoleon case. No matter how many crazy people think they are Napoleon, Napoleon’s own grounds for thinking he is Napoleon are different, and (arguably) the existence of those crazy people shouldn’t undercut his self-confidence. It would be very controversial, for example, to accept an indifference principle suggesting that if 10,000 crazy people have thought they are Napoleon, and if (hypothetically) Napoleon does or should know this about the world, then Napoleon himself should only believe he is Napoleon with a credence of 1/10,000. Of course, there are important disanalogies between the sims case and the Napoleon case. My point is only that your argument has a larger gap here than you seem to be granting.
[Regarding the response to B] Agreed. It’s an open question. I wouldn’t underplay the likelihood that many future sims might exist in short-term entertainments or single-mind AIs. I like your suggestion, though, that it might be impractical or impossible to have a solo sim with realistic non-conscious replicas as the solo’s apparent interactive partners – but that point will interact at least with the issue of sim duration. I’ve been solo in my office for half an hour. If I’m a short-duration sim, then probably non-conscious quantities AI will have been sufficient to sustain my illusion of a half-hour’s worth of internet interactions with people. How the openness of the duration/solo question plays out argumentatively might depend on one’s argumentative purposes. For purposes of establishing the sims possibility the non-trivial likelihood of the existence of massive ancestor simulations is sufficient. But for purposes of evaluating the practical consequences of accepting the sims possibility, it might be important to bear in mind that many sims may not exist in long-duration, high-population sims. It seems to me that unless you can establish that most sims do live in long-duration, high-population sims, the sims possibility has more skeptical consequences, and perhaps more of a normative impact on practical reflection, than you suggest.
[Regarding the possible interaction between (B) and (C)] I agree with your reasoning in faq 4. Just to be clear, what I was suggesting in my comment on the interaction between (B) and (C) was not intended as an objection of the sort posed in faq 4. In fact, the second of the two connections I remark on seems to increase the probability that I am a sim (and secondarily, to a lesser extent, that we are sims) by reducing the probability of DOOM/PLATEAU.
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Bostrom's Response to My Follow-Up:
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[On Issue A] That was intended as a continuity argument rather than a slippery slope argument. I’m not saying one point should be regarded as equivalent to another point because there is a smooth slope between them, but rather that credence should vary continuously as the underlying situation varies continuously. Is the alternative that I should assign credence 1 to being in a sim conditional on everybody being in a sim, but credence 0 to being in a sim conditional on there being at least one person like me who is not in a sim? Would an analogous principle also hold if we imagine that a single individual could be taken in and out of a simulation on alternating days without noticing the transfer? Folks willing to bet according to those obstinate odds would then soon deplete their kids’ college funds.
(For more background, see e.g. http://www.anthropic-principle.com/preprints/cos/big2.pdf.)
[On Issue B] I broadly agree with that. Pending further information, it seems the simulation hypothesis should lead us to assign somewhat greater probability than we otherwise would to a range of outlier possibilities (including variations of solipsism, creationism, impending extinction, among others). To go beyond that, I think one needs to start to think specifically about what motives advanced civilizations might have for creating simulations (and one should then be diffident but not necessarily completely despairing about our ability to figure out the motives of such presumably posthuman people). The practical import of the simulation hypothesis is thus perhaps initially relatively slight but it might well grow as our analysis advances enabling us to see things more clearly.
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