Though to be honest, I am having trouble seeing what the difference is between this statement being true and being false.
My argument for that is essentially structured as a dissolution of “existence”, an answer to the question “Why do I think I exist?” instead of “Why do I exist?”. Whatever facts are related to one’s feeling of existence — all the neurological processes that lead to one’s lips moving and saying “I think therefore I am”, and the physical processes underlying all of that — would still be true as subjunctive facts about a hypothetical mathematical structure. A brain doesn’t have some special existence-detector that goes off if it’s in the “real” universe; rather, everything that causes us to think we exist would be just as true about a subjunctive.
This seems like a genuinely satisfying dissolution to me — “Why does anything exist?” honestly doesn’t feel intractably mysterious to me anymore — but even ignoring that argument and starting only with Occam’s Razor, the Level IV Multiverse is much more probable than this particular universe. Even so, specific rational evidence for it would be nice; I’m still working on figuring out what qualify as such.
There may be some. First, it would anthropically explain why this universe’s laws and constants appear to be well-suited to complex structures including observers. There doesn’t have to be any The Universe that happens to be fine-tuned for us; instead, tautologically, we only find ourselves existing in universes in which we can exist. Similarly, according to Tegmark, physical geometries with three non-compactified spatial dimensions and one time dimension are uniquely well-suited to observers, so we find ourselves in a structure with those qualities.
Anyway, yeah, I think there are some good reasons to believe (or at least investigate) it, plus some things that still confuse me (which I’ve mentioned elsewhere in this thread and in the last section of my post about it), including the aforementioned “infinite ethics problem of awesome magnitude”.
A brain doesn’t have some special existence-detector that goes off if it’s in the “real” universe; rather, everything that causes us to think we exist would be just as true about a subjunctive.
This seems to lead to madness, unless you have some kind of measure over possible worlds. Without a measure, you become incapable of making any decisions, because the past ceases to be predictive of the future (all possible continuations exist, and each action has all possible consequences).
Measure doesn’t help if each action has all possible consequences: you’d just end up with the consequences of all actions having the same measure! Measure helps with managing (reasoning about) infinite collections of consequences, but there still must be non-trivial and “mathematically crisp” dependence between actions and consequences.
No, it could help because the measure could be attached to world-histories, so there is a measure for “(drop ball) leads to (ball to fall downwards)”, which is effectively the kind of thing our laws of physics do for us.
There is also a set of world-histories satisfying (drop ball) which is distinct from the set of world-histories satisfying NOT(drop ball). Of course, by throwing this piece of world model out the window, and only allowing to compensate for its absence with measures, you do make measures indispensable. The problem with what you were saying is in the connotation, of measure somehow being the magical world-modeling juice, which it’s not. (That is, I don’t necessarily disagree, but don’t want this particular solution of using measure to be seen as directly answering the question of predictability, since it can be understood as a curiosity-stopping mysterious answer by someone insufficiently careful.)
I don’t see what the problem is with using measures over world histories as a solution to the problem of predictability.
If certain histories have relatively very high measure, then you can use that fact to derive useful predictions about the future from a knowledge of the present.
I don’t see what the problem is with using measures over world histories as a solution to the problem of predictability.
It’s not a generally valid solution (there are solutions that don’t use measures), though it’s a great solution for most purposes. It’s just that using measures is not a necessary condition for consequentialist decision-making, and I found that thinking in terms of measures is misleading for the purposes of understanding the nature of control.
You said:
Without a measure, you become incapable of making any decisions, because the past ceases to be predictive of the future
I guess the difference that is relevant here is that if it is false, then a “real” person generates subjective experience, but a possible person (or a possible person execution-history) doesn’t.
“Infinite ethics” is surely a non-problem for individuals—since an individual agent can only act locally. Things that are far away are outside the agent’s light cone.
This is an all-possible-worlds-exist philosophy. There are an infinite number of worlds where there are entities which are subjectively identical to you and cognitively similar enough that they will make the same decision you make, for the same reasons. When you make a choice, all those duplicates make the same choice, and there are consequences in an infinity of worlds. So there’s a fuzzy neoplatonic idea according to which you identify yourself with the whole equivalence class of subjective duplicates to which you belong.
But I believe there’s an illusion here and for every individual, the situation described actually reduces to an individual making a decision and not knowing which possible world they’re in. There is no sense in which the decision by any one individual actually causes decisions in other worlds. I postulate that there is no decision-theoretic advantage or moral imperative to indulging the neoplatonic perspective, and if you try to extract practical implications from it, you won’t be able to improve on the uncertain-single-world approach.
By hypothesis. There is no evidence for any infinities in nature. Agents need not bother with infinity when making decisions or deciding what the right thing to do is. As, I think, you go on to say.
I agree. I was paraphrasing what ata and Roko were talking about. I think it’s a hypothesis worth considering. There may be a level of enlightenment beyond which one sees that the hypothesis is definitely true, definitely false, definitely undecidable, or definitely irrelevant to decision-making, but I don’t know any of that yet.
There is no evidence for any infinities in nature. Agents need not bother with infinity when making decisions or deciding what the right thing to do is.
I think, again, that we don’t actually know any of that yet. Epistemically, there would appear to be infinitely many possibilities. It may be that a rational agent does need to acknowledge and deal with this fact somehow. For example, maximizing utility in this situation may require infinite sums or integrals of some form (the expected utility of an action being the sum, across all possible worlds, of its expected utility in each such world times the world’s apriori probability). Experience with halting probabilities suggests that such sums may be uncomputable, even supposing you can rationally decide on a model of possibility space and on a prior, and the best you can do may be some finite approximation. But ideally one would want to show that such finite methods really do approximate the unattainable infinite, and in this sense the agent would need to “bother with infinity”, in order to justify the rationality of its procedures.
As for evidence of infinities within this world, observationally we can only see a finite distance in space and time, but if the rationally preferred model of the world contains infinities, then there is such evidence. I see this as primarily a quantum gravity question and so it’s in the process of being answered (by the ongoing, mostly deductive examination of the various available models). If it turns out, let us say, that gravity and quantum mechanics imply string theory, and string theory implies eternal inflation, then you would have a temporal infinity implied by the finite physical evidence.
There’s no temporal infinity without spatial infinity (instead you typically get eternal return). There’s incredibly weak evidence for spatial infinity—since we can only see the nearest 13 billion light years—and that’s practiacally nothing—compared to infinity.
The situation is that we don’t know with much certainty whether the world is finite or infinite. However, if an ethical system suggests people behave very differently here and now depending on the outcome of such abstract metaphysicis, I think that ethical system is probably screwed.
If this is in some sense true, then we have an infinite ethics problem of awesome magnitude.
Though to be honest, I am having trouble seeing what the difference is between this statement being true and being false.
My argument for that is essentially structured as a dissolution of “existence”, an answer to the question “Why do I think I exist?” instead of “Why do I exist?”. Whatever facts are related to one’s feeling of existence — all the neurological processes that lead to one’s lips moving and saying “I think therefore I am”, and the physical processes underlying all of that — would still be true as subjunctive facts about a hypothetical mathematical structure. A brain doesn’t have some special existence-detector that goes off if it’s in the “real” universe; rather, everything that causes us to think we exist would be just as true about a subjunctive.
This seems like a genuinely satisfying dissolution to me — “Why does anything exist?” honestly doesn’t feel intractably mysterious to me anymore — but even ignoring that argument and starting only with Occam’s Razor, the Level IV Multiverse is much more probable than this particular universe. Even so, specific rational evidence for it would be nice; I’m still working on figuring out what qualify as such.
There may be some. First, it would anthropically explain why this universe’s laws and constants appear to be well-suited to complex structures including observers. There doesn’t have to be any The Universe that happens to be fine-tuned for us; instead, tautologically, we only find ourselves existing in universes in which we can exist. Similarly, according to Tegmark, physical geometries with three non-compactified spatial dimensions and one time dimension are uniquely well-suited to observers, so we find ourselves in a structure with those qualities.
Anyway, yeah, I think there are some good reasons to believe (or at least investigate) it, plus some things that still confuse me (which I’ve mentioned elsewhere in this thread and in the last section of my post about it), including the aforementioned “infinite ethics problem of awesome magnitude”.
This seems to lead to madness, unless you have some kind of measure over possible worlds. Without a measure, you become incapable of making any decisions, because the past ceases to be predictive of the future (all possible continuations exist, and each action has all possible consequences).
Measure doesn’t help if each action has all possible consequences: you’d just end up with the consequences of all actions having the same measure! Measure helps with managing (reasoning about) infinite collections of consequences, but there still must be non-trivial and “mathematically crisp” dependence between actions and consequences.
No, it could help because the measure could be attached to world-histories, so there is a measure for “(drop ball) leads to (ball to fall downwards)”, which is effectively the kind of thing our laws of physics do for us.
There is also a set of world-histories satisfying (drop ball) which is distinct from the set of world-histories satisfying NOT(drop ball). Of course, by throwing this piece of world model out the window, and only allowing to compensate for its absence with measures, you do make measures indispensable. The problem with what you were saying is in the connotation, of measure somehow being the magical world-modeling juice, which it’s not. (That is, I don’t necessarily disagree, but don’t want this particular solution of using measure to be seen as directly answering the question of predictability, since it can be understood as a curiosity-stopping mysterious answer by someone insufficiently careful.)
I don’t see what the problem is with using measures over world histories as a solution to the problem of predictability.
If certain histories have relatively very high measure, then you can use that fact to derive useful predictions about the future from a knowledge of the present.
It’s not a generally valid solution (there are solutions that don’t use measures), though it’s a great solution for most purposes. It’s just that using measures is not a necessary condition for consequentialist decision-making, and I found that thinking in terms of measures is misleading for the purposes of understanding the nature of control.
You said:
Ah, I see, sufficient but not necessary.
But smaller ensembles could also explain this, such as chaotic inflation and the string landscape.
I guess the difference that is relevant here is that if it is false, then a “real” person generates subjective experience, but a possible person (or a possible person execution-history) doesn’t.
“Infinite ethics” is surely a non-problem for individuals—since an individual agent can only act locally. Things that are far away are outside the agent’s light cone.
This is an all-possible-worlds-exist philosophy. There are an infinite number of worlds where there are entities which are subjectively identical to you and cognitively similar enough that they will make the same decision you make, for the same reasons. When you make a choice, all those duplicates make the same choice, and there are consequences in an infinity of worlds. So there’s a fuzzy neoplatonic idea according to which you identify yourself with the whole equivalence class of subjective duplicates to which you belong.
But I believe there’s an illusion here and for every individual, the situation described actually reduces to an individual making a decision and not knowing which possible world they’re in. There is no sense in which the decision by any one individual actually causes decisions in other worlds. I postulate that there is no decision-theoretic advantage or moral imperative to indulging the neoplatonic perspective, and if you try to extract practical implications from it, you won’t be able to improve on the uncertain-single-world approach.
Re: “There are an infinite number of worlds”
By hypothesis. There is no evidence for any infinities in nature. Agents need not bother with infinity when making decisions or deciding what the right thing to do is. As, I think, you go on to say.
I agree. I was paraphrasing what ata and Roko were talking about. I think it’s a hypothesis worth considering. There may be a level of enlightenment beyond which one sees that the hypothesis is definitely true, definitely false, definitely undecidable, or definitely irrelevant to decision-making, but I don’t know any of that yet.
I think, again, that we don’t actually know any of that yet. Epistemically, there would appear to be infinitely many possibilities. It may be that a rational agent does need to acknowledge and deal with this fact somehow. For example, maximizing utility in this situation may require infinite sums or integrals of some form (the expected utility of an action being the sum, across all possible worlds, of its expected utility in each such world times the world’s apriori probability). Experience with halting probabilities suggests that such sums may be uncomputable, even supposing you can rationally decide on a model of possibility space and on a prior, and the best you can do may be some finite approximation. But ideally one would want to show that such finite methods really do approximate the unattainable infinite, and in this sense the agent would need to “bother with infinity”, in order to justify the rationality of its procedures.
As for evidence of infinities within this world, observationally we can only see a finite distance in space and time, but if the rationally preferred model of the world contains infinities, then there is such evidence. I see this as primarily a quantum gravity question and so it’s in the process of being answered (by the ongoing, mostly deductive examination of the various available models). If it turns out, let us say, that gravity and quantum mechanics imply string theory, and string theory implies eternal inflation, then you would have a temporal infinity implied by the finite physical evidence.
There’s no temporal infinity without spatial infinity (instead you typically get eternal return). There’s incredibly weak evidence for spatial infinity—since we can only see the nearest 13 billion light years—and that’s practiacally nothing—compared to infinity.
The situation is that we don’t know with much certainty whether the world is finite or infinite. However, if an ethical system suggests people behave very differently here and now depending on the outcome of such abstract metaphysicis, I think that ethical system is probably screwed.
That is something the MP’s preceding sentence seems to indicate.