They are called “interpretations” and not “theories” for a reason: they are designed to make no new testable predictions. I don’t know what untestable musings can say about the nature of reality, as opposed to the nature of the person doing the musing.
If I interpret “reality” as “the underlying causality I am part of” rather than “what my future sense data is going to be” then untestable statements about reality are totally possible, and can be very action-relevant, for example in making decisions that only have effects after I die. It is possible to form very-likely-true beliefs about many of these statements using considerations such as parsimony and symmetry.
I don’t understand what “the underlying causality I am part of” can possibly mean, since causality is a human way to model observations. This statement seems to use the mind projection fallacy to invert the relationship between map and territory.
untestable statements about reality are totally possible, and can be very action-relevant, for example in making decisions that only have effects after I die
Obviously. There is a good model of what happens after you die. It has been tested many times on other people. This has nothing to do with untestability of interpretations, which all predict the same thing, because they use the same mathematical formalism.
It is possible to form very-likely-true beliefs about many of these statements using considerations such as parsimony and symmetry.
Not really parsimony or symmetry as main considerations. What you use is a model of the world that has been proven reliable in the past. Parsimony and symmetry are just some ideas that were useful in constructing this model. E.g. “when a person dies, the world continues to exist” and “I am a person” are both testable models. Sure, there are models like “I’m a special snowflake”, but they generally don’t survive the contact with observations.
Re causality: In context I mean something like: there is a world that I am part of, and it evolves over something similar to time, with “future” things depending on “past” things. (The issue with time is that causality seems more fundamental than time; there can be multiple consistent assignments of times to the same causal structure, e.g. in the theory of relativity). Unless you are a solipsist or otherwise think the territory is unreferencable I am not sure how we could disagree on this? I suppose you could believe that things at different “times” exist and that things at “times immediately in the future” always satisfy some law with respect to the “previous” things, but that they don’t depend on “past” things (scare quotes to indicate that time isn’t fundamental); this leads to the same conclusions with respect to the things under discussion.
Re stuff that happens after you die: “This is what happens after other people die, therefore it will happen after I die” is an appeal to symmetry. The statement “the world continues to exist after I die” can’t be tested; similar statements (“the world continues to exist after Bob dies”) can be tested but they are not equivalent to the statement in question.
Similarly, “Small parts of the world evolve according to quantum mechanics, therefore large ones do too” is an appeal to symmetry; this statement implies that there is no such thing as “wavefunction collapse” (except perhaps a universal wavefunction collapse) and in particular consciousness can’t cause collapse.
Re parsimony and symmetry: what do you think of the grue/bleen problem? Parsimony and symmetry both offer easy answers to this problem, but how do you make sensible predictions without appealing to either of these or to very similar things?
Most of these ideas are of the type of “what happens to a spaceship when it goes beyond the cosmological horizon?” and the answer is pretty standard: we build models which work well in certain situations and we apply them to all situations where they are reasonably expected to work, even if we sometimes don’t get to see the results first-hand. You can call it parsimony or symmetry, but the order is reversed: you first build a working model, then apply it wherever it makes sense and adjust or replace as needed where it is outside its domain of applicability based on new observations. In the cases where the observations are not available, you take a chance, but generally not a huge one. For example, there might be a topological domain wall just outside the cosmological horizon, but there are no indications of this being the case given what we know about the universe.
The question of where a model is expected to generalize and where it isn’t is the entire problem. You are taking expectations about generalization as basic; I argue that these expectations are based on considerations of parsimony and symmetry. The order isn’t reversed here; parsimony/symmetry give rise to intuitions about whether a model will generalize.
The argument that no collapse happens at intermediate scales between very small and the entire universe is a symmetry-based argument, just as the argument that things beyond the cosmological horizon still exist is a symmetry-based argument.
The argument that no collapse happens at intermediate scales between very small and the entire universe is a symmetry-based argument, just as the argument that things beyond the cosmological horizon still exist is a symmetry-based argument.
Yes, I agree. But to discover and effectively apply symmetry one generally has to have a workable model first. For example, the invariance of the speed of light followed from the Maxwell equations, and was confirmed experimentally, and was incorporated in the math of the Lorentz transformations, yet without a good theory those appeared ugly, not symmetric. It took a new theory to reveal the hidden symmetry. And to eventually write the Maxwell equations in half a line, []A=J and divA=0, down from the original 20. Same with the cosmological horizon: it does not appear symmetric and one needs to understand some amount of general relativity to see the symmetry. Or believe those who say that there is one. The “no collapse at the intermediate scales” is a good hypothesis, but quite possible wrong, because gravity is likely to cause decoherence in some way, as Penrose pointed out.
I agree with most of the things you are saying here. I am not sure I agree about the cosmological horizon; it seems like you could derive this from special relativity, but in any case this is a minor point. I don’t know enough physics to confirm the thing you said about gravity and collapse.
In any case it seems you are currently saying “no collapse at intermediate scales is a good hypothesis and maybe wrong for this specific reason” whereas initially you were saying “interpretations [of quantum mechanics] by definition make no difference” and “I don’t know what untestable musings can say about the nature of reality”, and these statements seem to be in tension (as the question of whether collapse happens at intermediate scales depends on what are currently called “interpretations of quantum mechanics”, and is currently untestable); do you still agree with your original statements?
Yes, you could derive the horizon stuff from special relativity, but to construct an asymptotically de Sitter spacetime you need general relativity. Anyway, that wasn’t the original issue. “no collapse at intermediate scales is a good hypothesis and maybe wrong for this specific reason” is one possibility, the likelihood of which is currently hard to evaluate, as it extrapolates quantum mechanics far beyond the domain where it had been tested (Zeilinger’s bucky ball double slit experiments). The nature of the apparent collapse is a huge open problem, with decoherence and Zurek’s quantum Darwinism giving some hints at why certain states survive and others don’t, and pretending that MWI somehow dissolves the issue, the way Eliezer tells the tale, is a bit of a delusion. Anyway, MWI does not make any predictions, since it simply tells you that the feeling of being in a single world is an illusion, without going into the details of how to resolve the Wigner’s friend and similar paradoxes. See Scott Aaronson’s lecture 12 on the topic for more discussion.
I don’t understand what “the underlying causality I am part of” can possibly mean, since causality is a human way to model observations. This statement seems to use the mind projection fallacy to invert the relationship between map and territory.
If you want to discount the use of causal models as merely a “human way to model observations” (one that presumably bears no underlying connection to whatever is generating those observations), then you will need to explain why they work so well. The set of all possible sequences of observations is combinatorially large, and the supermajority of those sequences admit no concise description—they contain no regularity or structure that would allow us to substantially compress their length without losing information. The fact that our observations do seem to be structured, therefore, is a very improbable coincidence indeed. The belief in an external reality is simply a rejection of the notion that this extremely improbable circumstance is a coincidence.
I think the correct claim around this topic is that interpretation may reflect moral judgement, and consequently decisions about what to do in a world seen under a given interpretation, which does say something about the person doing the musing, and could be very useful to them. Conversely, knowledge about reality is useful to a person only to the extent it helps them with decision making. So insisting on divesting theories of interpretation is good methodology with both upsides and downsides, not a fundamental principle, which is I’m guessing what some people hear when the distinction between theories and interpretations is pointed out.
They are called “interpretations” and not “theories” for a reason: they are designed to make no new testable predictions. I don’t know what untestable musings can say about the nature of reality, as opposed to the nature of the person doing the musing.
If I interpret “reality” as “the underlying causality I am part of” rather than “what my future sense data is going to be” then untestable statements about reality are totally possible, and can be very action-relevant, for example in making decisions that only have effects after I die. It is possible to form very-likely-true beliefs about many of these statements using considerations such as parsimony and symmetry.
See also No Logical Positivist am I.
I don’t understand what “the underlying causality I am part of” can possibly mean, since causality is a human way to model observations. This statement seems to use the mind projection fallacy to invert the relationship between map and territory.
Obviously. There is a good model of what happens after you die. It has been tested many times on other people. This has nothing to do with untestability of interpretations, which all predict the same thing, because they use the same mathematical formalism.
Not really parsimony or symmetry as main considerations. What you use is a model of the world that has been proven reliable in the past. Parsimony and symmetry are just some ideas that were useful in constructing this model. E.g. “when a person dies, the world continues to exist” and “I am a person” are both testable models. Sure, there are models like “I’m a special snowflake”, but they generally don’t survive the contact with observations.
Re causality: In context I mean something like: there is a world that I am part of, and it evolves over something similar to time, with “future” things depending on “past” things. (The issue with time is that causality seems more fundamental than time; there can be multiple consistent assignments of times to the same causal structure, e.g. in the theory of relativity). Unless you are a solipsist or otherwise think the territory is unreferencable I am not sure how we could disagree on this? I suppose you could believe that things at different “times” exist and that things at “times immediately in the future” always satisfy some law with respect to the “previous” things, but that they don’t depend on “past” things (scare quotes to indicate that time isn’t fundamental); this leads to the same conclusions with respect to the things under discussion.
Re stuff that happens after you die: “This is what happens after other people die, therefore it will happen after I die” is an appeal to symmetry. The statement “the world continues to exist after I die” can’t be tested; similar statements (“the world continues to exist after Bob dies”) can be tested but they are not equivalent to the statement in question.
Similarly, “Small parts of the world evolve according to quantum mechanics, therefore large ones do too” is an appeal to symmetry; this statement implies that there is no such thing as “wavefunction collapse” (except perhaps a universal wavefunction collapse) and in particular consciousness can’t cause collapse.
Re parsimony and symmetry: what do you think of the grue/bleen problem? Parsimony and symmetry both offer easy answers to this problem, but how do you make sensible predictions without appealing to either of these or to very similar things?
Most of these ideas are of the type of “what happens to a spaceship when it goes beyond the cosmological horizon?” and the answer is pretty standard: we build models which work well in certain situations and we apply them to all situations where they are reasonably expected to work, even if we sometimes don’t get to see the results first-hand. You can call it parsimony or symmetry, but the order is reversed: you first build a working model, then apply it wherever it makes sense and adjust or replace as needed where it is outside its domain of applicability based on new observations. In the cases where the observations are not available, you take a chance, but generally not a huge one. For example, there might be a topological domain wall just outside the cosmological horizon, but there are no indications of this being the case given what we know about the universe.
The question of where a model is expected to generalize and where it isn’t is the entire problem. You are taking expectations about generalization as basic; I argue that these expectations are based on considerations of parsimony and symmetry. The order isn’t reversed here; parsimony/symmetry give rise to intuitions about whether a model will generalize.
The argument that no collapse happens at intermediate scales between very small and the entire universe is a symmetry-based argument, just as the argument that things beyond the cosmological horizon still exist is a symmetry-based argument.
Yes, I agree. But to discover and effectively apply symmetry one generally has to have a workable model first. For example, the invariance of the speed of light followed from the Maxwell equations, and was confirmed experimentally, and was incorporated in the math of the Lorentz transformations, yet without a good theory those appeared ugly, not symmetric. It took a new theory to reveal the hidden symmetry. And to eventually write the Maxwell equations in half a line, []A=J and divA=0, down from the original 20. Same with the cosmological horizon: it does not appear symmetric and one needs to understand some amount of general relativity to see the symmetry. Or believe those who say that there is one. The “no collapse at the intermediate scales” is a good hypothesis, but quite possible wrong, because gravity is likely to cause decoherence in some way, as Penrose pointed out.
I agree with most of the things you are saying here. I am not sure I agree about the cosmological horizon; it seems like you could derive this from special relativity, but in any case this is a minor point. I don’t know enough physics to confirm the thing you said about gravity and collapse.
In any case it seems you are currently saying “no collapse at intermediate scales is a good hypothesis and maybe wrong for this specific reason” whereas initially you were saying “interpretations [of quantum mechanics] by definition make no difference” and “I don’t know what untestable musings can say about the nature of reality”, and these statements seem to be in tension (as the question of whether collapse happens at intermediate scales depends on what are currently called “interpretations of quantum mechanics”, and is currently untestable); do you still agree with your original statements?
Yes, you could derive the horizon stuff from special relativity, but to construct an asymptotically de Sitter spacetime you need general relativity. Anyway, that wasn’t the original issue. “no collapse at intermediate scales is a good hypothesis and maybe wrong for this specific reason” is one possibility, the likelihood of which is currently hard to evaluate, as it extrapolates quantum mechanics far beyond the domain where it had been tested (Zeilinger’s bucky ball double slit experiments). The nature of the apparent collapse is a huge open problem, with decoherence and Zurek’s quantum Darwinism giving some hints at why certain states survive and others don’t, and pretending that MWI somehow dissolves the issue, the way Eliezer tells the tale, is a bit of a delusion. Anyway, MWI does not make any predictions, since it simply tells you that the feeling of being in a single world is an illusion, without going into the details of how to resolve the Wigner’s friend and similar paradoxes. See Scott Aaronson’s lecture 12 on the topic for more discussion.
If you want to discount the use of causal models as merely a “human way to model observations” (one that presumably bears no underlying connection to whatever is generating those observations), then you will need to explain why they work so well. The set of all possible sequences of observations is combinatorially large, and the supermajority of those sequences admit no concise description—they contain no regularity or structure that would allow us to substantially compress their length without losing information. The fact that our observations do seem to be structured, therefore, is a very improbable coincidence indeed. The belief in an external reality is simply a rejection of the notion that this extremely improbable circumstance is a coincidence.
I think the correct claim around this topic is that interpretation may reflect moral judgement, and consequently decisions about what to do in a world seen under a given interpretation, which does say something about the person doing the musing, and could be very useful to them. Conversely, knowledge about reality is useful to a person only to the extent it helps them with decision making. So insisting on divesting theories of interpretation is good methodology with both upsides and downsides, not a fundamental principle, which is I’m guessing what some people hear when the distinction between theories and interpretations is pointed out.