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Snowyowl comments on Open Thread, August 2010 - Less Wrong
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Here's a thought experiment that's been confusing me for a long time, and I have no idea whether it is even possible to resolve the issues it raises. It assumes that a reality which was entirely simulated on a computer is indistinguishable from the "real" one, at least until some external force alters it. So... the question is, assuming that such a program exists, what happens to the simulated universe when it is executed?
In accordance with the arguments that Pavirta gives below me, redundant computation is not the same as additional computation. Executing the same program twice (with the same inputs each time) is equivalent to executing it once, which is equivalent to executing it five times, ten times, or a million. You are just simulating the same universe over and over, not a different one each time.
But is running the simulation once equivalent to running it ZERO times?
The obvious answer seems to be "no", but bear with me here. There is nothing special about the quarks and leptons that make up a physical computer. If you could make a Turing machine out of light, or more exotic matter, you would still be able to execute the same program on it. And if you could make such a computer in any other universe (whatever that might mean), you would still be able to run the program on it. But in such considerations, the computer used is immaterial. A physical computer is not a perfect Turing machine - it has finite memory space and is vulnerable to physical defects which introduce errors into the program. What matters is the program itself, which exists regardless of the computer it is on. A program is a Platonic ideal, a mathematical object which cannot exist in this universe. We can make a representation of that program on a computer, but the representation is not perfect, and it is not the program itself. In the same way, a perfect equilateral triangle cannot actually be constructed in this universe; even if you use materials whose length is measured down to the atom, its sides will not be perfectly straight and its angles will not be perfectly equal. More importantly, if you then alter the representation to make one of the angles bigger, it does not change the fact that equilateral triangles have 60° angles, it simply makes your representation less accurate. In the same way, executing a program on a computer will not alter the program itself. If there are conscious beings simulated on your computer, they existed before you ran the program, and they will exist even if you unplug the computer and throw it into a hole - because what you have in your computer is not the conscious beings, but a representation of them. And they will still exist even if you never run the program, or even if it never occurs to anyone on Earth that such a program could be made.
The problem is, this same argument could be used to justify the existence of literally everything, everywhere. So we are left with several possible conclusions: (1)Everything is "real" in some universe, and we have no way of ever finding such universes. This cannot ever be proved or falsified, and also leads to problems with the definition of "everything" and "real". (2)The initial premise is false, and only physical objects are real: simulations, thoughts and constructs are not. I think there is a philosophical school of thought that believes this to be true, though I have no idea what its name is. Regardless, there are still a lot of holes in this answer. (3)I have made a logical mistake somewhere, or I am operating from an incorrect definition of "real". It happens.
It is also worth pointing out that both (1) and (2) invalidate every ethical truth in the book, since in (1) there is always a universe in which I just caused the death of a trillion people, and in (2) there is no such thing as "ethics" - ideas aren't real, and that includes philosophical ideas.
Anyway, just bear this in mind when you think about a universe being simulated on a computer.
That's pretty much Tegmark's Multiverse, which seems pretty popular around here (I think it makes a lot of sense).
Indeed. I have a post making similar arguments, though I still haven't been able to resolve the ethical and anthropic problems it raises in any satisfactory way. At this point I've backtracked from the confidence I held when I wrote that post; what I'm still willing to say is that we're probably on the right track thinking of "Why does anything exist?" as a wrong question and thinking of reality as indexical (i.e. the true referent of the category "real" is the set of things instantiated by this universe; it is a category error to talk about other universes being real or not real), but the Mathematical Universe Hypothesis still leaves much to be confused about.
My own view is that (ignoring simulations for the time being) MWI ideas have no conflict with our usual ethical intuitions and reasonings. Yes, it is the case that when I choose between evil action A and good action B, there will be two branches of the universe - one in which I choose A and one in which I choose B. This will be the case regardless of which choice I make. But this does not make my choice morally insignificant, because I split too, along with the rest of the universe. The version of me that chose evil act A will have to live thereafter with the consequences of that choice. And the version of me that chose B must live with quite different consequences.
What, more than that, could a believer in the moral significance of actions want of his universe?
The situation with respect to simulations is a bit trickier. Suppose I am deciding whether to (A) pull the plug on a simulation which contains millions of sentient (simulated) beings, or (B) allow the simulation to continue. So, I choose, and the universe branches. If I chose A, I must live with the consequences. I don't have that simulation to kick around any more. But, if I were to worry about all the simulated lives that I have so ruthlessly terminated, I can easily reassure myself that I have only terminated a redundant copy of those lives. The (now) master copy of the simulation plays on, over in that parallel universe where I chose B.
Is it wrong to create a simulation and then torture the inhabitants? Well, that is an ethical question, whereas this is a meta-ethical analysis. But the meta-ethical answer to that ethical question is that if you torture simulated beings, then you must live with the consequences of that.
That's not how MWI works, unless human brains have a quantum randomness source that they use to make decisions (which does not appear to be the case).
I'm not sure it matters to the analysis. Whether we have a Tegmark multiverse, or Everett MWI with some decisions depending on quantum randomness and others classically determined, or whether the multiple worlds are purely subjective fictions created to have a model of Bayesianism; regardless of what you think is a possible reduction of "possibly"; it is still the case that you have to live in the reality which you helped to create by way of your past actions.
agreed, it's not like scientific analysis requires the laws of physics to have no quantum randomness source etc, rather it is satisfied with finding the logical necessities between what is used to describe the observable universe.
Now we do.
Yes, MWI ideas have no conflict with usual ethical intuitions. And they also help you make better sense of those intuitions. Counterfactuals really do exist, for example; they're not just some hypothetical that is in point of fact physically impossible.
but we shouldn't concern ourselves with counter factuals if they aren't part of our observed universe.
My impression is that sometimes we do need to deal with them in order to make the math come out right, even though the only thing we are really concerned about is our observed universe. Just as we sometimes need to deal with negative numbers of sheep - however difficult we may find this to visualize if we work as a shepherd.
true, but there are no 'negative sheep', only numbers arbitrarily representing them.
but we shouldn't concern ourselves with numbers if they aren't part of our observed universe.
numbers are quite useful, so we don't/shouldn't do away with them, but the math is never a complete substitute for the observable universe.
writing down '20 sheep' doesn't physically equal 20 sheep, rather it's a method we use for simplicity. as it stands, no two sheep are alike to every last detail as far as anyone can tell, yet we still have a category called 'sheep'. this is so given the observed recurrence of 'sheep' like entities, similar enough for us to categorize them for practicality's sake, but that doesn't mean they're physically all alike to every detail.
it could be argued that sometimes the math does equate with reality, as in 'Oxygen atom' is a category consisting of entirely similar things, but even that is not confirmed, simply an assertion; no human has observed all 'Oxygen atoms' in existence to be similar in every detail, or even in some arbitrarily 'essential' detail/s. yet it is enough for the purposes of science to consider them all similar, and so we go with it,otherwise we'd never have coherent thought let alone science.
it might very well be that all Oxygen atoms in existence are physically the same in some ways, but we have no way of actually knowing. this doesn't mean that there are 'individual atoms', but it doesn't negate it either.
ETA: as pengvado said in below post, replace 'atom' with 'particle'.
No Individual Particles. The fact that measurements of their mass/charge/etc have always come out the same, is not the only evidence we have for all particles of a given type being identical.
(A whole oxygen atom is a bad example, though. Atoms have degrees of freedom beyond the types of particles they're made of.)
Uhmm. I hate to explain my own jokes, but ... You did notice the formal similarity between my "we shouldn't concern ourselves" comment and its great grandparent, right?
True (only) in the sense that our numbers are part of our map and not the territory. In the same sense we have no way of actually knowing there are patterns in the universe appropriately named Oxygen. Or Frog.
I should add that it is impossible to erase your sin by deciding to terminate the simulation, so as to "euthanize" the victims of your torture. Because there is always a branch where you don't so decide, and the victims of your torture live on.
In some sense, maybe. But if that were generally true, then I wouldn't have any reason to run the same program twice, but I do. (for example, I have repeatedly asked my calculator what is 1080*4/3, since I have a weird TV and untrustworthy memory)
I don't think it works like that. Math is a conceptual construct, not something that has its own reality separate from either the thing it approximates or the mind that approximates with it.
I'm reminded of the person who thought that using the equations for relativistic rather than classical mechanics to model cannonballs would give the wrong answer.
Only things that happen are real. There's no Math Heaven inhabited by angelic equations in a separate magisterium from the world of the merely real.