Possibly I understand your outlook better now. For you, worlds are like hills in a landscape. You’re on one of them, there’s a local maximum, but there’s no need to demarcate exactly where one hill ends and another begins. What is real is the landscape.
You don’t experience a whole world, just a small part of one, so you are not epistemically compelled to think of whole worlds as sharply bounded entities. However, if you consider your own place in this ontology, you’re not just near a local maximum or on a local maximum, you are a local maximum, and here you no longer have the option of indeterminacy. Your experience definitely exists—it is, after all, the only reason you know that anything exists; it is, by hypothesis, not all that exists; and so, within That Which Exists, there is a sharp and objective distinction between That Which You Experience and That Which You Do Not Experience.
It should also be apparent that you don’t just exist or experience featurelessly; you are something, a particular entity, and you are experiencing something particular. This is what you are denying when you say that there are situations where there is no fact about what your state of consciousness is or even whether you have one. To which all I will say is that that is the ultimate in irrationalism. I can only guess that you are thinking of consciousness in “third person” terms, as a hypothesized entity which may or may not be posited (according to one’s theoretical preference) and whose nature is a matter of definition (and therefore potentially vague or conventional), rather than as the substance of everything you know and cannot deny, unless you wish to deny reality itself.
We shall see if this latest lecture of mine on the necessity of the objectivity of your existence makes an impression. But proceeding from that premise, it follows that, if you wish to maintain that reality in its totality is something like a universal wavefunction, you must find at least one sharply delineated entity in it, because you are a sharply delineated entity that exists, and you are not identical with the whole.
P.S. On the topic of relativity and QFT: It’s difficult to rigorously define the interacting field theories which physicists actually use in a self-contained way, because they probably only exist as equivalence classes of approximations to deeper trans-QFT theories (like superstring vacua). This is the contemporary understanding of the meaning of renormalization that emerged in the 1970s. You have an unknown self-contained theory whose low-energy behavior can be approximated by a finite number of parameters, and renormalizable QFTs are the language in which this approximation is expressed. They can’t be axiomatized as functionals over a space of field configurations, which then get approximated by a power series of Feynman diagrams. The most you can do is develop a formal algebra of these power series themselves. For a rather technical example of this (but worth a look if you want to see the real thing), see the latest paper by Richard Borcherds.
But assuming that string theory or some other framework removes that technical obstacle, what’s the status of my argument that relativity contradicts MWI? The argument does suppose that we are talking about exactly specified whole-universe worlds that “split” instantly on some hypersurface of simultaneity. I don’t see how any such model can avoid the “ontological gauge-fixing” I mentioned in the previous comment. The only alternatives I can see are (1) Gell-Mann and Hartle’s decoherent histories, which are self-contained (no splitting) and coarse-grained (lacking some properties by classical ontological standards), and (2) a hypothetical “blistering” model of world-splitting, where instead of being instantaneous along a preferred hypersurface, it starts at a point and a sheaf of new worlds peels away from the parent world in a local and causal way, with the blister spreading at light-speed. In this second model, one has to imagine the descendant worlds in the separating sheaf themselves beginning to blister and split even while the split that created them continues to propagate and grow, and so one has sheaves of part-worlds growing upon sheaves of part-worlds. A picture like that might be made ontologically relativistic in some complicated way. Each of these options introduces further issues, but I’ll leave them alone for now unless someone takes them up.
Thanks. This exchange really awakened me, not so much to the fact that MWI is ‘wrong’ (I still don’t think it is), but to the enormity of the philosophical challenge one faces in justifying it.
To clarify, there are two senses in which MWI could be ‘right’ or ‘wrong’.
(a) Do we in fact live in a multiverse?
(b) Could we have found ourselves in a multiverse? That is, in a hypothetical universe where objective physical reality is exactly as MWI theorists describe it, and supposing it contained structures that behaved like conscious observers, could we successfully predict ‘what it would be like’ to be those observers, and would it be ‘essentially’ like our own experiences (whatever we deem the ‘essential’ aspects of our experience to be)? (From my perspective, this is the same as asking: If you did a simulation of an MWI universe on an ordinary computer, would the ‘simulated beings’ have experiences like ours (in the relevant respects)?)
Leaving aside (a) for the moment, I think the ‘disconnect’ between our respective worldviews works out like this:
I think that, since nonrelativistic QM is a self-contained theory, if we’re given a model of this theory—a ‘toy universe’ if you like—it must be possible to deduce a priori what conscious observers there are in this universe, if any, and what they are conscious of (albeit with my usual caveat that we shouldn’t expect perfectly “sharp” answers.) If you accept this premise, then you don’t need to poison the ontological simplicity of MWI by adding ‘Worlds’, ‘Histories’ or ‘Minds’. All you need to do is carefully ‘unpack’ what’s already in front of you. (The “Bare Theory” is enough, modulo a lot of analytic reasoning.)
(This presupposes the truth of analytic functionalism.)
On the other hand, I suspect you regard it as obvious—so obvious that it should go without saying—that the Bare Theory isn’t enough. That the work you need to do in order to generate empirical predictions must be ‘synthetic’ rather than ‘analytic’. That bringing ‘many worlds’ to life requires axioms rather than mere definitions.
Your experience definitely exists—it is, after all, the only reason you know that anything exists; it is, by hypothesis, not all that exists; and so, within That Which Exists, there is a sharp and objective distinction between That Which You Experience and That Which You Do Not Experience.
Sorry but I’m unpersuaded. I mean, when a hill gets smaller it gradually and continuously loses its identity as a ‘thing’, to the local topographical variations around it. Likewise, the ‘boundary’ of a hill is somewhat indeterminate (just as the boundary of the Sun’s gravity well is somewhat indeterminate).
It should also be apparent that you don’t just exist or experience featurelessly; you are something, a particular entity, and you are experiencing something particular. This is what you are denying when you say that there are situations where there is no fact about what your state of consciousness is or even whether you have one. To which all I will say is that that is the ultimate in irrationalism.
The ultimate in irrationalism? To me those conclusions look unavoidable. Don’t Dennett’s examples make any impression on you? Consider change blindness: you’re alternately shown two slides A and B which depict the same scene, but with a significant alteration which under normal circumstances would ‘leap out at you’. But because there’s a short delay between presentations of A and B, the slides can be switched many times before you notice the difference. Then Dennett wants to say that there’s no ‘right answer’ to the question of whether, prior to noticing the change, your visual phenomena included the bit of the scene that was changing.
And doesn’t pointing out the inevitable arbitariness of any attempt to single out ‘the first appearance of consciousness in the tree of life’ cut any ice? To me it’s the most obvious thing in the world that there isn’t always a determinate answer to the question “is that thing conscious?” I honestly find it baffling that so many thinkers resist this conclusion.
For a rather technical example of this (but worth a look if you want to see the real thing), see the latest paper by Richard Borcherds.
Thanks for the reference—I’m always meaning to teach myself about this stuff.
User DZS has directed me to a paper which provides a relativistically covariant ontology for QFT! Consistent histories already had this, but the histories there can be arbitrarily sparsely specified. This ontology, “space-time state realism”, goes to the opposite extreme and it does so very ingeniously. It uses the “Heisenberg picture” of QFT rather than the “Schrodinger picture”. The Schrodinger picture is the usual one in which the state vector evolves in time and the operators do not. The Heisenberg picture is usually described as using a state vector which doesn’t evolve in time and operators which do; but the important fact, for the purposes of interpretation, is that the operators are associated to space-time points and so form a manifold-like set that can be relativistically transformed.
Operators are not yet states, however. What these authors (Wallace and Timpson) do, is to define a Hilbert space for an arbitrary space-time region, and then a way to construct a state in that Hilbert space, using data about how the field operators in that region behave with respect to the unique “initial” state used in the Heisenberg picture. So in their ontology, absolutely every space-time region and subregion (every open set, maybe? haven’t gone over the details) has a quantum state attached, in a way that is consistent across regions. It’s very clever, and it’s just enough overkill to guarantee that the true ontology is almost certainly hiding somewhere in there.
Possibly I understand your outlook better now. For you, worlds are like hills in a landscape. You’re on one of them, there’s a local maximum, but there’s no need to demarcate exactly where one hill ends and another begins. What is real is the landscape.
You don’t experience a whole world, just a small part of one, so you are not epistemically compelled to think of whole worlds as sharply bounded entities. However, if you consider your own place in this ontology, you’re not just near a local maximum or on a local maximum, you are a local maximum, and here you no longer have the option of indeterminacy. Your experience definitely exists—it is, after all, the only reason you know that anything exists; it is, by hypothesis, not all that exists; and so, within That Which Exists, there is a sharp and objective distinction between That Which You Experience and That Which You Do Not Experience.
It should also be apparent that you don’t just exist or experience featurelessly; you are something, a particular entity, and you are experiencing something particular. This is what you are denying when you say that there are situations where there is no fact about what your state of consciousness is or even whether you have one. To which all I will say is that that is the ultimate in irrationalism. I can only guess that you are thinking of consciousness in “third person” terms, as a hypothesized entity which may or may not be posited (according to one’s theoretical preference) and whose nature is a matter of definition (and therefore potentially vague or conventional), rather than as the substance of everything you know and cannot deny, unless you wish to deny reality itself.
We shall see if this latest lecture of mine on the necessity of the objectivity of your existence makes an impression. But proceeding from that premise, it follows that, if you wish to maintain that reality in its totality is something like a universal wavefunction, you must find at least one sharply delineated entity in it, because you are a sharply delineated entity that exists, and you are not identical with the whole.
P.S. On the topic of relativity and QFT: It’s difficult to rigorously define the interacting field theories which physicists actually use in a self-contained way, because they probably only exist as equivalence classes of approximations to deeper trans-QFT theories (like superstring vacua). This is the contemporary understanding of the meaning of renormalization that emerged in the 1970s. You have an unknown self-contained theory whose low-energy behavior can be approximated by a finite number of parameters, and renormalizable QFTs are the language in which this approximation is expressed. They can’t be axiomatized as functionals over a space of field configurations, which then get approximated by a power series of Feynman diagrams. The most you can do is develop a formal algebra of these power series themselves. For a rather technical example of this (but worth a look if you want to see the real thing), see the latest paper by Richard Borcherds.
But assuming that string theory or some other framework removes that technical obstacle, what’s the status of my argument that relativity contradicts MWI? The argument does suppose that we are talking about exactly specified whole-universe worlds that “split” instantly on some hypersurface of simultaneity. I don’t see how any such model can avoid the “ontological gauge-fixing” I mentioned in the previous comment. The only alternatives I can see are (1) Gell-Mann and Hartle’s decoherent histories, which are self-contained (no splitting) and coarse-grained (lacking some properties by classical ontological standards), and (2) a hypothetical “blistering” model of world-splitting, where instead of being instantaneous along a preferred hypersurface, it starts at a point and a sheaf of new worlds peels away from the parent world in a local and causal way, with the blister spreading at light-speed. In this second model, one has to imagine the descendant worlds in the separating sheaf themselves beginning to blister and split even while the split that created them continues to propagate and grow, and so one has sheaves of part-worlds growing upon sheaves of part-worlds. A picture like that might be made ontologically relativistic in some complicated way. Each of these options introduces further issues, but I’ll leave them alone for now unless someone takes them up.
Thanks. This exchange really awakened me, not so much to the fact that MWI is ‘wrong’ (I still don’t think it is), but to the enormity of the philosophical challenge one faces in justifying it.
To clarify, there are two senses in which MWI could be ‘right’ or ‘wrong’.
(a) Do we in fact live in a multiverse?
(b) Could we have found ourselves in a multiverse? That is, in a hypothetical universe where objective physical reality is exactly as MWI theorists describe it, and supposing it contained structures that behaved like conscious observers, could we successfully predict ‘what it would be like’ to be those observers, and would it be ‘essentially’ like our own experiences (whatever we deem the ‘essential’ aspects of our experience to be)? (From my perspective, this is the same as asking: If you did a simulation of an MWI universe on an ordinary computer, would the ‘simulated beings’ have experiences like ours (in the relevant respects)?)
Leaving aside (a) for the moment, I think the ‘disconnect’ between our respective worldviews works out like this:
I think that, since nonrelativistic QM is a self-contained theory, if we’re given a model of this theory—a ‘toy universe’ if you like—it must be possible to deduce a priori what conscious observers there are in this universe, if any, and what they are conscious of (albeit with my usual caveat that we shouldn’t expect perfectly “sharp” answers.) If you accept this premise, then you don’t need to poison the ontological simplicity of MWI by adding ‘Worlds’, ‘Histories’ or ‘Minds’. All you need to do is carefully ‘unpack’ what’s already in front of you. (The “Bare Theory” is enough, modulo a lot of analytic reasoning.)
(This presupposes the truth of analytic functionalism.)
On the other hand, I suspect you regard it as obvious—so obvious that it should go without saying—that the Bare Theory isn’t enough. That the work you need to do in order to generate empirical predictions must be ‘synthetic’ rather than ‘analytic’. That bringing ‘many worlds’ to life requires axioms rather than mere definitions.
Sorry but I’m unpersuaded. I mean, when a hill gets smaller it gradually and continuously loses its identity as a ‘thing’, to the local topographical variations around it. Likewise, the ‘boundary’ of a hill is somewhat indeterminate (just as the boundary of the Sun’s gravity well is somewhat indeterminate).
The ultimate in irrationalism? To me those conclusions look unavoidable. Don’t Dennett’s examples make any impression on you? Consider change blindness: you’re alternately shown two slides A and B which depict the same scene, but with a significant alteration which under normal circumstances would ‘leap out at you’. But because there’s a short delay between presentations of A and B, the slides can be switched many times before you notice the difference. Then Dennett wants to say that there’s no ‘right answer’ to the question of whether, prior to noticing the change, your visual phenomena included the bit of the scene that was changing.
And doesn’t pointing out the inevitable arbitariness of any attempt to single out ‘the first appearance of consciousness in the tree of life’ cut any ice? To me it’s the most obvious thing in the world that there isn’t always a determinate answer to the question “is that thing conscious?” I honestly find it baffling that so many thinkers resist this conclusion.
Thanks for the reference—I’m always meaning to teach myself about this stuff.
User DZS has directed me to a paper which provides a relativistically covariant ontology for QFT! Consistent histories already had this, but the histories there can be arbitrarily sparsely specified. This ontology, “space-time state realism”, goes to the opposite extreme and it does so very ingeniously. It uses the “Heisenberg picture” of QFT rather than the “Schrodinger picture”. The Schrodinger picture is the usual one in which the state vector evolves in time and the operators do not. The Heisenberg picture is usually described as using a state vector which doesn’t evolve in time and operators which do; but the important fact, for the purposes of interpretation, is that the operators are associated to space-time points and so form a manifold-like set that can be relativistically transformed.
Operators are not yet states, however. What these authors (Wallace and Timpson) do, is to define a Hilbert space for an arbitrary space-time region, and then a way to construct a state in that Hilbert space, using data about how the field operators in that region behave with respect to the unique “initial” state used in the Heisenberg picture. So in their ontology, absolutely every space-time region and subregion (every open set, maybe? haven’t gone over the details) has a quantum state attached, in a way that is consistent across regions. It’s very clever, and it’s just enough overkill to guarantee that the true ontology is almost certainly hiding somewhere in there.