Comments on: Philosophy in the Newspapers

By: Jamie

Jamie — Wed, 28 Jul 2004 17:18:13 +0000

If we assume you are material, then you can show that you are material? What an odd argument. Brian is not trying to demonstrate that he is a material being. (If anyone doubts that he is one, I am willing to swear out an affidavit.) He is responding to Bostrom’s argument. Bostrom’s conclusion was not that Brian is immaterial. An argument to the conclusion that Brian is a material being would be questionbegging if it took as a premise that he is one. That’s obvious. It is not obvious that it is question-begging to use that premise in the present argument. It may be, but it’s not obvious. That would take some showing.

By: Monica

Monica — Wed, 28 Jul 2004 14:00:56 +0000

“assume, as I’m going to do until someone gives me a proof that I shouldn’t, that I’m material…So there’s no obvious statistical argument that I should be uncertain whether I’m material unless we start filling up the reference classes with beings that I know I am not.” If we assume you are material, then you can show that you are material? What an odd argument. Or perhaps I need to go read your paper.

By: matt

matt — Wed, 28 Jul 2004 13:45:25 +0000

Evidence may not be phenomenal, but belief is, is it not? In which case, our belief both about the evidence and about the implications of that evidence could be identical to those of simulations. In which case, it’s still relevant.

By: John Quiggin

John Quiggin — Wed, 28 Jul 2004 08:58:26 +0000

Brian, I’m not clear about the claim here. You are asserting that we know we are material beings. If so, it seems obvious that we are not simulees and no probabilistic argument is going to change this. But what about the simulees? It seems to me there are two possibilities (i) they know they are not material (ii) they falsely believe they are material [unlike the simulees they themselves have created] Are you asserting one of these, or something else completely?

By: Brian Weatherson

Brian Weatherson — Wed, 28 Jul 2004 02:42:36 +0000

Matt, your (a) and (b) are true, but why do they matter? We in fact can tell material things from simulations, so why does it matter that people with very different evidence to ours cannot tell this. If you thought evidence was all phenomenal and they are in the same phenomenal state we are I could understand the worry. But why think that?

By: Matt

Matt — Wed, 28 Jul 2004 01:10:54 +0000

To counter the second part of your argument, wouldn’t one only have to change the description of a state as simply “indiscriminable from” another state to, “is indiscriminable from, and lacks the ability to recognize this indiscriminability?” Take your analogy as an example: at 2 martinis, I can recall having 2 martinis, but at 4, I may recall having had 2 martinis, or 3, or 5. I have no idea that my memory abilities are (temporarily) diminished. Now imagine that we are, in fact, simulations. It might be the case (and, I suspect it would be easy to argue that it is the case) that we a.) would not be able to tell whether we are, in fact, simulations or materials, and b.) would not be able to recognize that we cannot actually determine the facts of the situation. This would have the effect of making our belief, and our belief that we can distinguish between the two states, irrelevant to the question of whether we are in fact material.

By: Brian Weatherson

Brian Weatherson — Tue, 27 Jul 2004 21:17:12 +0000

On John’s point, the idea here is that Descartes was engaged in the wrong project. We simply don’t have to be able to justify our beliefs to a determined sceptic in order for it to be true that they are justified. Descartes presupposes that we do, but there’s no reason for this, and nothing but trouble seems to come from accepting it. I take it Bostrom’s argument is meant to show something stronger. It is meant to show that with just making ordinary presuppositions about the actual world we can call into question our belief that we are material beings. And that’s what I’m arguing against. And that’s why I’m fully prepared to use the fact that we are actually material in my defence. If I was trying to argue with the sceptic this would be question-begging. (Arguments with the sceptic seem to always end up question-begging.) But since I’m just objecting to a particular argument, I’m allowed to use assumptions I bring to the table unless and until the arguer has shown me they are false. That’s why, pace Thomas, it’s not question-begging in this context to say that I have mostly reliable beliefs. Sure they aren’t perfect, but they are way better than the guy in the simulation. I wasn’t making the assumption Monica thinks I was making. Here was the argument there less compressed. Assume, as I think is plausible, that nothing in the universe has experiences from which mine are indiscriminable (by me). And assume, as I’m going to do until someone gives me a proof that I shouldn’t, that I’m material. Then the proportion of beings in the universe with experiences from which mine are indiscriminable is 1. So there’s no obvious statistical argument that I should be uncertain whether I’m material unless we start filling up the reference classes with beings that I know I am not. And there’s no reason to fill up the reference classes that way. (And if we do there are so many ways to fill them up that we get inconsistent results – but that’s another story.) There’s a simpler case to show that indiscriminability is asymmetric. I can tell, just by looking and feeling, that I’m not a rock. I can discriminate my experiences from those a rock has. (I’m assuming here that rocks don’t have conscious states. If not we have to really rethink our ethics.) But a rock can’t discriminate anything, hence it can’t discriminate its state from mine. Now some might say this is a special case because the rock has no discriminating power at all, but I think it’s just an extreme case of a fairly standard kind of situation. On John’s point, the worry here isn’t that the simulees experience is ‘coarser’ than ours. The worry is that thinking about what we have in common with simulees underestimates how much information we have about the world. There’s a picture Bostrom (and Descartes, and many other philosophers) are working with that our evidence about the external world starts and ends with our phenomenal experiences. That’s just what is being denied here. (Daniel is right that it’s a kind of externalism, though more like Austin’s and his followers than Nozick’s.) There’s a difference of type between us and the simulee – we can see tables, chairs and beer mugs and they can’t. And since what one can see is part of ones basic evidence about what the world is like, we have a different kind of evidence to what they do. (If, as always, we are actually material. If we are simulations then all bets are off.) Since we aren’t even in the same kind of epistemic situation as the simulees, making more and more of them, or making hierachies of them, doesn’t particularly change our epistemic situation.

By: Daniel Elstein

Daniel Elstein — Tue, 27 Jul 2004 17:43:51 +0000

I think that you’re wrong about indiscriminability being asymmetric. Your example is not convincing, because I’m inclined to say that if you really can’t tell that you’re drunk when you’re drunk then you can’t tell that you’re sober when you’re sober either. I take it that the moral of the example is just that we can tell when we’re drunk (though it may be a little tricky) just as pace Descartes we can tell when we’re dreaming. It seems that the substantive point in your argument is meant to depend on some form of epistemic externalism – when you say that as material beings we have the ability to form reliable perceptual beliefs. I thought that no such strategy had a hope of defeating sceptical arguments precisely because of the indisciminability point – that was (I thought) what Edward Craig showed in his article ‘Nozick and the Sceptic’ (Analysis 1989).

By: Scott Martens

Scott Martens — Tue, 27 Jul 2004 15:33:04 +0000

There are a number of problems with the question of whether or not the universe is a simulation, but they’re not so easily dismissed. First, I originally heard the question a little differently: Imagine that computer technology progresses and we become able to simulate the universe. We then do so, for entertainment and scientific value. Inevitably, we do so repeatedly. What are the odds, given these stipulations, that we are living in one of the simulations? It’s a goofy question, but I started thinking about it. First, Daniel Wolpert proved back in the 80’s that an accurate simulation of any space which contains the computer doing the simulating must run slower than the real universe. This follows as a correlary of the Halting Problem, but it applies to any type of physically realisable machine, not just Turning machines. Thus, simulating an entire universe within a universe of comparable size possessed of the same laws of physics – and thus the same ability to build computers within subspaces of the same size – means that the simulated universe must run more slowly than the real universe. In the limiting case, the simulated universe runs on a computer which takes up the entire universe, and may therefore approach running just as fast. But if so, no one can live outside the simulation. Alternately, if the simulated universe has different laws of physics, which either forbid the construction of computers with the same level of problem solving ability as the simulators, or which allow computers of identical power, but requires that they take greater volume to build, then the real universe is measurably different from the simulated one. It has different physics. In that case, either we live in the real universe or we live in a simulation built by aliens – we might as well call them gods – but there is no chance that it is either the one or the other, because we can know that there is a real difference between the two, and that if we knew what that difference was, we could know which we were in. The simulation is not indistinguishable from the real thing, it’s just that we can’t be sure we’re not in the simulation and have never seen the real world. The same applies to the case where the simulated universe is smaller than the real universe. Once again, there would be a real difference between the two, even if we don’t know which one we’re in. Lastly, I considered one possiblity for how one might distinguish a simulated universe from the real one: physics at different scales. A simulated universe can not have scale-invariant laws of physics. A real universe might. Scale-invariant laws of physics would require an infinite amount of computing power to simulate. The existence of scale-invariant laws of physics is a scientific theory in the Popperian sense. It is not a metaphysical supposition. It would be easy to falsify: identify a scale at which the laws of physics change, so that no new theory could account for physical activities at both the macro and micro scale. In a simulation that uses finite computing power and runs in finite time such a level must exist. The contrary, however, is harder to show. Scale variant physics is a necessary property of simulated universes. It is not necessarily true that real universes must have scale invariant physics.

By: lindley

lindley — Tue, 27 Jul 2004 13:34:54 +0000

This might be a naive question… but, in the paper, what is the difference between the “creedence” Cr(.|.) formulation, and something like “subjective probability?” That is, when the paper says that proposition (##) is “for all Phi, Cr(Phi | frequency(Phi)=x) = x”, how is this different from a subjective belief, with some basic exchangeability argument? And doesn’t that make the First, Second, and Third “Interpretations” just refutations of a mis-understanding of conditioned probabilities? (i.e., Pr(x | y) means you’re conditioning on y, and that Pr(x) is conditionally independent, given y, of all other ‘knowledge’ you may possess?)

By: John Quiggin

John Quiggin — Tue, 27 Jul 2004 13:26:25 +0000

Sorry, I missed Matt’s comment making the same point.

By: John Quiggin

John Quiggin — Tue, 27 Jul 2004 13:24:18 +0000

Here’s a version of Bostrom that seems robust to your refutation. Suppose we create simulees whose experiences are very similar to ours, but coarser in some way we can detect and they cannot. By hypothesis, they also create coarser simulees and so on ad infinitum or to levels we can’t observe. Now there’s no way for us to tell that we aren’t at some intermediate point in a sequence of this kind. We can represent the problem by a set of integers, arbitrarily large but bounded above, in which, if n and n-1 are in the set, n-1 is a simulee generated by n. Then our chance drawing the first number is 1/N which can be arbitrarily small.

By: John Quiggin

John Quiggin — Tue, 27 Jul 2004 13:16:45 +0000

What would Descartes say about this? Having first concluded that his existence is robust to the simulee hypothesis, he eventually uses the goodness of God (proved in intermediate steps) to reject it. But if we suppose a world in which everyone can be an omnipotent deceiver, and many people are, it’s hard to see how Descartes would make his case.

By: Monica

Monica — Tue, 27 Jul 2004 13:00:34 +0000

Yeah, I’m with Thomas and Matt. In addition, there’s another problem with your refutation: it hinges on assuming that if sets of experiences are unique, such that no two beings share them, then all beings are material. How in the world do you get that?

By: lambda

lambda — Tue, 27 Jul 2004 12:13:41 +0000

Re: Java, Javascript, and VM’s… Not to get too pedantic, but the technical way of saying this is: “Java” (a different language from Javascript, sharing only the name and some syntactic similarities in common) is compiled into an intermediate language (“bytecode,”) which is then interpreted by the V(irtual) M(achine). The term ‘machine’ is applied here because bytecode looks a lot like the low-level instructions that are interpreted by the hardware (chip) in your computer… and so you can think of the VM as an idealized form of a ‘register machine’ (actually, in this case, a ‘stack machine,’ but ok). Javascript, is a language which is ‘interpreted’ by your browser… but there’s nothing unique about the browser being able to do that. I could just as easily write a stanadlone app that interprets JS, or build a browser with an integrated VM. The only real difference, at a high level, is the intermediate compilation step that Java (typically) goes through… but it would be just as easy to write a javascript interpreter that used an intermediate compilation stage, or a Java “VM” that interpreted the language without compilation. So theoretically, the Java VM and the ‘interpreter’ embedded in your browser are the same thing… they’re both ‘evaluating’ an artificial language, and ‘showing’ you the result… All the rest of the terminology (in addition to the decision to call it a “VM” in the first place) is basically marketing-speak. sorry to interrupt; please resume the original discussion….