Transcript discussion Hawthorne

July 21 9.30
A metaphysician looks at the Everett interpretation
Speaker: John Hawthorne
Commentator: James Ladyman
Floor speakers (in order of appearance)
Hartle
Albert
Hemmo
Saunders
Albrecht
Wallace
Janssen
Bacciagaluppi
Loewer
Papineau
Timpson
Maudlin

87

Comment by – Ladyman

1. Right, well there’s loads in there. I’d just like to start by saying something general which I planned to say because I didn’t know what John was going to say and I had to plan something. And that was that I thought it would be helpful – some of the discussion I don’t think has been clear about what the Everettian is required to do, or what people are taking the Everettian to be required to show. So, first of all, distinguish three things you might believe as an Everettian. One, you might believe just that the Everett picture is coherent as an interpretation of quantum mechanics, that would be the weakest egg?. The Next thing you might believe is: the Everett picture is actually the best interpretation of quantum mechanics. And the third thing you might believe is: there are multiple universes. Now, it seems to me that a lot of people might go to the second without necessarily going to the third. So, those are the things that you could believe, now what about the burden of proof that is on the Everettian? Well, it’s a familiar point in lots of areas of philosophy that one doesn’t require the adherent of a view always to convert the devout sceptic. So an Everettian might say, look, it’s not my job to show that, given the empirical evidence you ought to believe in Everett, you ought to believe in branching universes. They might say it’s just my job to show that, given that I’m an Everettian, my position is coherent.

2. Now, I think we can similarly distinguish – moving on to what John was talking about – two different versions of his second question. So, I think it’s quite right to distinguish two things, one is what’s the fundamental story about the world and, two, how do we recover the familiar macroscopic world from the fundamental story. But there’s a weaker and stronger or harder and easier version of the second task, so, the hard version is – which I think some of John’s criticisms traded on, presupposing this is the right version of the task – is to say: if you were just given the fundamental description of the world you ought to be able to read off from it the familiar macroworld. I think David [Wallace] explicitly distanced himself from that task in his remarks on day one. I think what David was saying is you don’t perhaps have to be able to get the familiar macroscopic categories out of the fundamental description without putting anything in. It’s rather that you want to show how, given that you’re already equipped with you macroscopic categories, your everyday categories like tiger, cat, whatever, you can make sense of how you’re managing to use them given the fundamental description. That’s obviously a weaker job to set yourself to do. Now, I just wanted to make an analogy there and it’s an obvious one to make but it’s one that we haven’t talked about so much apart from maybe it comes up in what Jim Hartle was saying. Simon, long and illuminating, made the analogy between the block universe of special relativity and the block universe of the Everett picture and the analogy is, well, a particular foliation of spacetime into space plus time is analogous to a branch and, just as with the special relativistic revolution we realised that all the foliations are on all fours, so in the Everett picture we realise that all the branches are on a par. In both cases you can see that there’s the same problem arising. It’s one thing to declare that the flow of time, and that our experience of events of coming in succession and of there being a particular foliation of spacetime is not fundamental; it’s another thing to submit that you can’t say that in some sense it’s not part of reality because our perception of reality is itself part of reality and so you’d better recover that it seems to us that there is a flow of time and a particular foliation, and that’s just what is going on when you try to recover branches, right.

3. But now here’s a disanalogy and this relates to vageness which John also talked about. David has this lovely paper called ‘Worlds in the Everett Interpretation’ there he says that there’s a direct correspondence, lots of things you can say about foliations you can also say about branching. But one thing you can say about foliations is that they’re not vague whereas branches do seem to be ineliminably vague and that seems to be an important disanalogy and one question I wanted to float was just, if we think about the familiar discussions of vagueness (or familiar to some of us, in philosophy) then, there are different theories of vagueness, one of them is epistemic theory of vagueness which Tim Williamson advocates, according to which, whilst our use doesn’t suffice to determine what the precise boundaries between the correct application of a vague predicate and incorrect application are, nonetheless there is an underlying fact about – and I’m probably getting this view wrong and being too crude about it but, roughly speaking, saying that vagueness is epistemic, it’s just down to our not knowing what the boundary is. And I think that might be an important disanalogy with those kinds of vagueness. In the case of branches it’s built into the story that that epistemic view is not available. That’s not a criticism, it’s just something I wanted to float.

4. …. .the region with vim, I thought – people who say that Bohm theory’s Everett in disguise or something like that, you might think, you might make an analogy between vim and the corpuscle, right, so those people who are rude about Bohm’s theory say it’s just like that, right, it’s just like putting vim into some of the trajectories. Now I’ll just finish by saying something about the structuralism – what John had that. I didn’t understand why, having made the distinction, which I would’ve that was quite a good distinction to make, between the conservative and the liberal ways of approaching John’s second question, that is, recovering the everyday world from the fundamental picture; why John thought that the Oxonian Everett project is committed to the conservative view. I thought quite the opposite, that it’s committed to the liberal view. So, on the conservative view, just to remind you, John said you’re going to try to identify familiar everyday objects with objects in the fundamental picture, and I took it that David precisely didn’t want to do that so I think that’s something that could be discussed.

5. So, just to go back to this business about the fundamental story; I’m suspicious of this metaphor of God giving us the fundamental story, and let me just finish by raising a kind of general sceptical note about what we could achieve with the Everett interpretation. If we like to think of the wave function applying to the whole universe the obvious question that arises is, well – you can do it as a joke – you can say “I know the complete state of the universe, here it is, psi. There you are. I’ve told you everything”. What you want to know when someone does that – you want to say “No, that’s not telling me anything until you write psi in a particular basis, and then I get information by seeing the amplitudes of the particular eigenstates in that basis. But now I just worry, well, what is a basis? Well, it’s associated with measurements that you can make, but how could you make a measurement of the whole universe? I mean, it looks like there’s one subsystem and what you do when you when you make a measurement is you correlate its states with the states of the target system. So what would it be to make a measurement of the whole universe? Well, there’d be nothing outside the universe to get correlated with the universe to measure it. So then what basis could we expect the fundamental wave function to be written in? One thought you might have is that philosophers might think, well, who cares about epistemologically, metaphysically theres some natural set of predicates and, analogous to that, you might think there just is a natural basis for the wave function of the universe. At that point you might think, well, suppose there is a wavefunction of the whole universe and suppose there is some operator that corresponds to the complete description of that state of the whole universe, then why couldn’t it be an open question whether or not the wavefunction of the universe was in an eigenstate of that operator. And if it was in an eigenstate of that operator then the whole universe wouldn’t be in branches even though it might look, if you looked at a bit of the universe, as if there were branches.

6. I should finish there, but also, I didn’t find it that crazy to think that I might be a real number. I mean, I don’t know what real numbers are; I don’t know what I am, so it would seem to be an open question. I’m pretty sure I’m not an integer or rational.

Hartle
7. [ gaps here due to very soft speaking, would be difficult to recover] Well, there were two separate talks this morning .....[very softly spoken] ….. I want to know …… in contemporary physics it seems ………. It’s much worse than the situation you have …….. there are all the other infinite possible people here .. in a sense? .. ……… a theory which had nothing to do with everyday descriptions of classical terms, tables and chairs, cats, human beings. And if you look a little further in physics, say to string theory, we’re getting even more exotic because we have … one thousand , a billion, an infinite number of so-called vacua which might conceivably describe the world, most of which have nothing to do with the world which we see. Physics seems to be moving further and further away the everyday at the fundamental level, for better or worse. So it’s less and less consistent with what I think you call metasemantical principles. So what will you say if this trend goes on for the next hundred years and then you’re looking at a … world with no … will you still maintain these metasemantical principles which are in conflict with extant physics? Or will you modify them?

Hawthorne
8. I don’t have anything very informative to say. The exotical thing was a bit tentative. I don’t want you to think that that’s the same thing as I was calling the metasemantical principles. I think this metasemantics stuff – it’s a foundational part of the story about how we’re located in the world. I don’t you can blow it off, as well – it’s just all garbage metasemantics – but on the other hand it’s methodologically very hard to know how to figure out which principles are true or not. I could perfectly well imagine that our changing vision of the contours of physical reality might in some way interact with, you know – just to take an example, if it turns out that causation as we normally think about it isn’t a very important part of the world then really leaning on causation in your account of how words get hooked onto the world might start to look very naïve; that’s just and example. So I’m not dogmatic in the way that you suspect here.

Albert
9. This is just a tiny point. I think this was a really helpful talk for things that we all need to think about in connection with these questions. There’s just one little piece I was confused by. You were talking about this model of thinking of a point floating around in a Hilbert space which you referred to as the Marvellous Point ….. something else at the Marvellous Point. That’s not actually a model that

Hawthorne
10. I wasn’t saying it’s a model you go for. There reason I was using it was that it’s an example of a model which in some sense you logically could go for that would suck. The way that the real number version sucks. So that’s

Albert
11. This ‘Marvellous Point’ term is actually used within the discussions to refer to something in a configuration space

Hawthorne
12. Yes, yes; I probably was misleadingly suggested that maybe you have something to do with this …… I don’t know, so sorry.

Hemmo
13. …. Interesting talk, there are a lot of things to think about here but I just wanted to … one specific point …….[extremely faint] …… that’s the vagueness of the branching – think also James said – maybe I don’t get it, exactly what is the intended status of the branching in the Everett picture. Let me just – I think about the fundamental book of nature – what I want to get at is that I’m not sure there’s any need for vagueness in the interpretation in the context of branching …… because, if you think about the overall – I mean just in elementary quantum mechanics, you think about the universal wave function of the whole universe; God knows it, so he knows the complete microphysical … about the world. He also knows exactly how we are structured. He knows the Hamiltonian, the actual Hamiltonian; then, He can figure out exactly – the way we interact with the environment, everything is spelt out clearly and there need be no vagueness in that picture. And so if branching is true, if the Everett theory is true then there need be no vagueness. The only kind of vagueness that would enter in is in the way we now use natural language and describe – we use natural language predicates and describe the world in a vague? Way, that’s fine. But that’s not fundamental, it’s just – you can push the vagueness completely into the language, natural language tokens, and there’s nothing fundamental

Hawthorne
14. Let’s just get that – it’s perfectly consistent, the Oxford picture, is at least consistent – it’s perfectly consistent to say that God could write a precise world book and the branch description of reality is inevitably vague and I gave you, at least very schematically, a model of how that would go. Suppose God knows the universal state perfectly; the way He’d describe it perspicuously is as some complex scalar field over configuration space. That’s the fundamental story, and when you look at the fundamental story there’s not in any fundamental way fission going on, but then the Oxford Everettians notice that on the hypothesis that the world’s like that, there is a course rough-and-ready way of parcelling up configuration space via rough-and-ready decoherence heuristics into parcels. But if that’s the way that branching talk has to be understood, and the heuristics that you use are inevitably course and rough-and-ready, then the way that you slap that onto the fundamental book of the world will be inevitably vague. And I should just say in passing that – I’m not sure that epistemicism versus non-epistemicism is too important here. I think even if you’re and epistemicist you could tell a story that goes from the premiss that branch talk is vague to the branch description isn’t fundamental, because even for the epistemicist you, as it were, need a range of candidates and if there’s a branch structure at the absolute rock bottom then there isn’t a range of candidates for branching. That’s just to tell you guys, the ones of you who haven’t thought about vagueness, it’s not so important to go in for the inference from it’s vague to there’s no fact of the matter. There are broader issues here, but they’re not guilty of some conflation –

Hemmo
15. My question is; I don’t understand why the thought is that there must be vagueness. That’s all.

Hawthorne
16. You’re asking the wrong guy….

Saunders
17. You’ve got a two worlds, okay, and a world they are qualitatively indistinguishable by any possible means of observaevaluation,ng but because something differs by one over ten to the power googleplex you have to count them as two, …. between them, okay, now who says that’s the right number? it’s got to ………say,ah, okay, there’s two …….one over the power googleplex isn’t small enough, maybe it’s not big enough, ………..

Hawthorne
18. Let’s make it more vivid better. Suppose there’s interference between

Saunders
19. Why should there be a fact of the matter about that?

Hemmo
20. If there is a difference between these two worlds….

Saunders
21. Sure, one over ten to the power googleplex, is that big enough, is it sufficient…

Hawthorne
22. Can I just make something vivid. Suppose there’s a bunch of objects and there’s interference between them all but there’s little bits of interference between some and lots of interference between others and basically you want to count – the rough-and-ready idea is that you want to count things as belonging to the same world if there’s lots of interference between them but in some cases that just simplifying; if there’ super-low interference then its okay to count them as parts of different worlds, but then you realise that the God’s description how different levels of interference – He’s not gonna care about what you’re going to count as – there’s going to be a familiar Sorites kind of structure where you’ve got all sorts of different levels of interference but our ways of individuating worlds requires arbitrarily selecting some level of interference

Hemmo
23. …….but you’re talking always from our point of view, I’m just

Hawthorne
24. What do you mean ‘our’ point of view? I’m talking from God’s point of view. I see all this interference, I see these people walking around talking about worlds, I can see they’re vaguely getting at some cut-off in interference levels, but it’s just like balls?

Hemmo
25. But you forgot something which is extremely important here. God knows exactly how we are structured ..

Hawthorne
26. Yes, he knows what the world is structured…

[hubbub]

Albrecht
27. I claim that an Everettian never has to count worlds. If you ask for answers to physics questions in the Everettian picture you never have to count worlds, you never have to worry about this googleplex.

[new question]

Wallace
28. [missed passages faint and quick, little chance of recovering them]…..a couple of little points, I think …with John against Meir’s point…talk about worlds, I mean, the inflation rate of the UK economy is a perfectly real and salient feature of the world but God ………………wouldn’t know precisely the inflation rate of the British economy, so I don’t think we need to worry about the verdict on exotic worlds, it’s totally ubiquitous across …..In terms of the more substantial criticisms or worries that remain about structuralism, and about where this fits on the conservative/liberal points of view. I think this ….you brought up about your Gallilean spacetime field models by saying where I think we would be on this. Suppose your Gallilean model has two fields and you just go by ..[names?].for example…………..the strategy for saying…….within as spacetime region is no longer available to us because we have to say which field ….What ……..something rather like what you then said we do in configuration space ……..feature; spacetime region or the wavefunction or ….classical field or whatever, and the thing about features, as a trivial point, I think, about features is …..they’re possibly less in danger of our doing a modal slight of hand ……though I don’t mind very much if they did anyway…… What counts as features, what are the salient features, the criteria for that I think again as James is pointing out, kind of top-down things in various ways . So I’m not sure…..conservative or liberal, it’s a kind of ignorance of the fact that all there is is the features of the microphyisical stuff, the salient features, the important features are the macrophysical features…[cross talk]……I think as far as the kind of structuralist worry that was coming up …..to some extent I would plead ignorance on the answer to that. I mean we know that – unless all hell is going to break loose some sort functionalist strategy is going to have to be sustained in some way, shape or form as to what the rules are. From the naturalistic perspective ……actually does, the constraint seems to be something like it needs to look kind of not cooked-up in terms of the theories fundamental variables. I mean, Dennett …………………………situation……...situation, doesn’t really address…..perhaps? tacitly that finding structure in a certain case …..building the all the structure into the code isn’t okay. I don’t know what the ……way of treating that story is and to be honest I just plead a kind of naturalistic confidence that there will be such a story because science seems to work that way. But as a last comment on that, the one thing I think it won’t be is intuitive or based on what we ………that’s one concern I have about your ……..issue, that what makes ……candidates, I’m slightly worried …..more intuitive candidates, I’m not sure …….there. The last very quick comment is …….you say you woudn’t be surprised if you found in the quantum states these exotica and all sorts of weird things, I don’t …….but I’d be very surprised……It’s supposed to be in the Everett picture a robust discovery about the theory…..world, that it contains an awful lot of this very high-level complex strucure. If it turns out that by squinting in different ways we see structure anyway we’er in…trouble so I think that if there really were widespread ….all over the place the theory really would be in trouble. And I don’t think it could be a minor worry or quibble; but I also think ……………want to say about occasional? .alternative structures like Simon talked about before might be a different matter.

Hawthorne
29. A couple of quick things. I suspect that people, this is just a suspicion, haven’t tried much squinting slightly different ways to see if they can find exotica, but it would be great if they’d tried and failed but it might be nice to try and see what you come up with as a sort of little bit of a methodological test. Definitely, I was relying on the – something more like the cooked-up heuristic rather than the intuitive …heuristic in the stuff that I was saying at the end. You know, fancied up a little bit in the Lewisian scheme where you have some objective ranking that’s precisely not anthropocentric of which properties in the world are cooked-up and which properties in the world aren’t cooked-up and then the idea is, well, if you start associating predicates with pretty gerrymandered things, then that’s bad. And then my only point was there’s inevitably going to be something symptomatically wrong to say if these things are tigers without the extras then they’re still gonna be tigers with the extras because it might perfectly well be that the extras trump the old candidates in terms of cooked-upness, however that’s fleshed out.

[new question]

Janssen
30. I wanted to follow up what Jim Hartle was saying, that were general comments. So basically, the whole ….about this distinction between fundamental theory and everyday experience. Metaphysicians worry about, well, let’s try to make that those two things are not going to drift from one another because we get in all sorts of philosophical trouble when we do that, right. So …. that you give like ….gaps…exotica.. they seem to be driving in that direction. I think as a scientist you’re just playing a very, very different game. And I think there the situation is – you hit upon this beautiful new theory; there’s a lot of empirical evidence that, look, we have this new theory of quantum mechanics, right, and it’s the painful realisation that something like that is going to have to replace the old comfortable Newtonian mechanics, and so now lets .[noise].with that. And for a scientist, and I’m not sure if I’m speaking for Jim Hartle but I’d hope so, - our evidence is telling us that this is it, right, and so unfortunately now we’re gonna have to build up and recover from that all these everyday things, and it ain’t going to be perfect, and that’s just the usual situation . Michael Turner? …cosmologists introduced what I think is a very beautiful phrase about this: scientists tend to be forward-engaged, they constantly take advantage of …..shucks?, it still needs to be developed in order to work out the scheme.

31. So just to pull in a few other things; when Simon Saunders was saying in response to ….well, if ..[noise]…all these problems that you’re talking about – be easier if it were just sort of billiard ball ontology or something; Simon quite correctly pointed out look, this is an historical artifact, right, go back to the seventeenth century corpuscularian philosophy, this seems to be very odd. Everybody understands this because everybody laughed at the joke yesterday …..saying, like, first we had Newton’s incomprehensible action at a distance and then we had Maxwell’s incomprehensible denial of action at a distance. This seems to be a typical thing to me and so the frustration I have listening to this talk and listening to Tim’s talk is that it seems like the bottom line is science ain’t metaphysics.

Hawthorne
32. Okay, well, I’m glad to see you worked up. Let’s calm down slightly and let me touch on a few points. By the way, I didn’t intend anything in what I said to betray some strong allegiance to a naïve early modern copuscularian view – what did I say that sounded like that? I thought I was being totally new-age then I get accused of

Janssen
33. ……[cross talk, noise]… but then there’s this very strong claim, for instance, well we all agree it would be completely nuts to think that we’re all like numbers.

Hawthorne
34. ..all like numbers. No, no; you didn’t understand what I said, I didn’t say it was nuts to think we’re all isomorphic to numbers – I said it’s nuts to think that reality is just real numbers and sets of real numbers and that’s the only things that there are. I don’t think you understood what I said. That is nuts. I think if you understood that

Janssen
35. I don’t think that is nuts

Hawthorne
36. Really? I don’t believe you

Janssen
37. ……..situation where your best scientific theory is pointing

Hawthorne
38. No, no; you’ll never ever find a physicist - ….[crosstalk]…… Can I just make one other point, trying to be less polemical. What you find in the history of these discussions is – you get a scientific theory and philosophers cum metaphysicians cum philosophers of science know this slightly different accounts of the world that are, as it were, in the spirit of that scientific theory. So the configuration space model and the Hilbert space model and the Simon Saunders model are all fundamental theories in the spirit, in the ball park, of the Everettian picture of the world which thinks of branches as vague. They’re all in that – And what you find in the history of philosophy is philosophers, a bit more than working physicists, and fair enough, they care a little bit more about which of those particular versions of the theory are most plausible and elegant, natural, simple, compelling and they’re also much more careful and sensitive and interested in the question of how our ordinary ways of talking are made true by that fundamental description of reality. And then they in fact come to know much better than physicists know metasemantics is fundamental to an understanding of our place in the physical world. And I don’t see where in anything that I’ve just said there’s a naivety or some backward thinking and in fact the only way of getting off the boat is a way of getting off the boat that super-scientifically-minded people have tried and failed which is by trying to say, well, although the fundamental stories are just notational variants and going super-instrumentalist but, you know, philosophers have tried that, they failed dismally, and so we’re back to that old game and history seems to have proven it’s a legitimate foundational and compelling one.

Wallace
39. …just briefly – having invited a metaphysician to come and talk about the Everett interpretation we shouldn’t be criticising him for talking about metaphysics.

[new question]

Bacciagaluppi
40. …..the contrast here ….is about which direction or explanation seems more natural and if fact where ………one direction of explanation is, starting from structure, dynamical symmetries ..give you a way of reconstructing the geometry of spacetime and then Ockam’s razor, you know, postulates spactime as a separate metaphysical entity and then trying to explain the dynamical symmetries from that and in fact I just don’t see how that explanation is supposed to work. There’s no way of forcing the dynamics to have a certain symmetry without postulating extra principles that should link this geometry with the physics. And, in fact, I think, and this is something that ….in Tim’s talk, the correct strategy for a Bohmian is to say the copuscularian description is explanatorily autonomous, everything you’re going to want to explain is going to be phrased in those terms, we have to deflate? .the reality of the wavefunction if we want to get a nice ….picture at the Bohmian level.. Two opposite intuitions about what’s more explanatory…..

[Hawthorne regards as remark rather than questiondoesn’t respond]

[new question]

Loewer
41. One thing about the functionalist programme ……..is that functionalism ..[noise]..very heavy use of causation. We don’t find causation in the fundamental physics. At some point it has to be introduced and it’s very, very puzzling how this can be introduced into the …physics without it ……….we won’t be able to give an account of tigers drooling? .without having……..

Ladyman
42. could I comment on that. Do you think you have to have causation in fundamental physics or do you think you have to have law?..

Loewer
43. No, I don’t think you do have to have causation in fundamental physics…

Ladyman
44. So suppose you thought that causation was associated with, you know, you had to already have a foliation of spacetime because something about causation involves things going in time, causes preceeding their effects and so on. You might think, okay, insofar as fundamental physics is not going to be preferring a particular foliation and presupposing passage, then it’s not going to feature causation. But then you might think, well, if there was some kind of law over and above regularity in fundamental physics then, once we added foliations and however we get time, then we get causation out of that.

Loewer
45. I don’t think it’s an issue whether it’s regularity or not. I mean Lewis has a big programme giving an account of laws as a sort of regularity account and a big programme for generating causation out of laws….counterfactuals…..but that programme hasn’t been successful so far. I was just pointing out that the functionalist program depends on getting something like causation……….

Hawthorne
46. I think things get up and running pretty well if you – don’t think of the functional thing initially in causal terms, just think there are, you know, tiger-shaped things then when they’re close to mouse-shaped things often the mouse-shaped things turn into mouse-archipelagoes, for example. If you could get all that going then you’re at least up and running, so I think the spirit in which David’s [Wallace] talking about functionalism is not primarily insisting on, as it were, the functionalist bit in the philosophy of mind where there’s a really big causal emphasis. Importantly, in the Dennett story, the ‘real pattern’ story, it doesn’t quite have a causal emphasis either, as an account of beliefs and desires, so – I’m not saying that would solve everything but it would at least …

Loewer
47. You said ‘close to’, so you’ve got a guy spatially…

Hawthorne
48. Right, you do get space, so I do think you need tiger-shaped things in a low-dimensional space and mouse-shaped things in a low-dimensional space, but I think Tim’s worries, for example, would be appeased a great deal if you could show how there’s a really salient and natural and non-cooked-up way to build a low-dimensional space with mouse-shaped and tiger-shaped things out of the ultimate configuration-theoretic story. I do agree there’d be these additional concerns, especially if you’re a conservative, as to where counterfactuals and this and that are coming from but

Loewer
49. .. these things have…

Hawthorne
50. And actions, yes, yes.

[new question]

Papineau
51. I wanted to talk about the explanatory gaps. So, I believe ……….when it comes to consciousness …..brute identities ….I don’t see why you thought that there was such a gap between the configuration space representation and something familiar

Hawthorne
52. Did you see with the real number case – you did see why there’s an explanatory gap there?

Papineau
53. I think that’s a bad model. Just think of ……suppose you’ve got two point-particles moving around in three-space and somebody says, oh, that’s a point moving around in six-space. Well, it’s a kind of clever-tricky? thing to say but I don’t have an explanatory gap between that claim, that fact,

Hawthorne
54. Say that again.

Papineau
55. I don’t have an explanatory gap between someone who says two points moving around in three-space is one point moving around in six-space. What’s going on? This guy’s found an economical way of representing the same fact and once I understand how this way of talking works I can see a priori it’s the same fact.

Hawthorne
56. I think you’ve got to be even very careful there. If your fundamental description, the six-space, doesn’t in any privileged way group the dimensions into threes then you start to really worry. So, I’m not saying that David’s programme is gonna fail, I’m saying – and I think David’s very sensitive to this- you know it is very tricky in that case and you can naively think, hey, this is just a six-space with no privileging and

Papineau
57. But in that case there is privileging and we understand it. Now there may be special reasons when we come to a multi-dimensional configuration space as in the Everettian theory why this is a good analogy, but you didn’t give us any special reasons…

Hawthorne
58. I really want to bear down on this six-dimensional thing because I think it is a good test case. So you start realise there is something very artificial and gerrymandered about describing this two-particle system if, in the laws and the structure there’s no privileging, there’s no bundling of dimensions into threes. And then you realise, hey, for this to work now at the fundamental layer of description we’re not going to have two particles and it not to seem more cooked-up we’re going to have to have fundamental laws or non-Lewisian laws or fundamental properties that group together the dimensions, and then you want to say what those properties look like and ask yourself “are these the sorts of things that we’d’ve liked all along or are these awkward, artificial labels for what we wanted at the end of the day rather than plausible posits about the fundamental structure of the world”. And I think it gets more tacky? but there’re exactly analogous issues that come up in the configuration space story and David’s bet is that there’ll be features that don’t look artificial that make one particular, or at least one vaguely related class of interpretations very much less cooked-up than other candidate interpretations. That’s the bet of the Oxford Everettians.

Timpson
59. I agree exactly with what you were saying just then, but I want to make a points on the positing of exotica and the danger of ending up with ….don’t want. Clearly there will be some naturalness constraints and the laws will probably play a big role in ……the exact structure of the laws, as you said …[noise] … Humean laws ..play that kind of role. But I did just want to …..a bit the posit here because I think there’s a way in which nobody can be positing this extra stuff because, they’re writing down theories about it; at best they’re being complacent about it. So there I don’t see that the sort of Quinian-inspired strictures on what would be a good theory and so on come into play because the fundamental theory is just a wavefunction theory on its own and if you want to recover our experiences then, yeah, we want quasi-classical theories which tell us what’s going on. So those are the only good theories using Quine’s sort of dictum. We are positing, at least when we’re reading off from the fundamental theory the other stuff, ………….and things like that ..we’re not positing the ……because nobody cares about the …….so we put strictures on theory choice then which then applies to that; so I think we ……complacency about it rather than positing it…

Hawthorne
60. I do think it’s quite delicate the ……thing and it’s the bit that I was not quite straight about. But let me give you analogy, and there are some philosophers who have asked themselves how he microphysics fixes consciousness and then they’ve come up with bridge principles that , you know, we are more or less conscious more or less as we think, but then they also have the result that carrots are conscious. So David Lewis thinks carrots have conscious experience. Now, David Chalmers thinks carrots have conscious experience; writing in 1811 this guy Tupper wrote a book on the possibility of sensation in vegetables ……Now I take it if we had a theory like that and said, look, Quineian strictures only apply at the fundamental level and its just got the wavefunction at the fundamental level, you know, I’ve got conscious carrots but Quineian strictures don’t apply there, we can be liberal in how we ……so long as we get the things we positively …. There seems to be something God-awful about the carrots-have-sensations bridge rules. I mean it’s a bit hard to articulate; get straight on what’s so bad about those, that’s the kind of prohibition on exotica I want but I’m not very straight on it

Timpson
61. ….the crucial thing is like using the conscious predicate which features in the ….theory and ….theory, whereas I guess I was thinking that the kind of junk you get the decoherent but non-classical histories just don’t have any of the same predicates at all

Hawthorne
62. Well ….in flatland there is a predicate. There are two-dimensional physical beings moving around a two-dimensional plane all their lives. And I don’t think it’s a good thing – Hey, I’m going to stipulate that the word ‘spacetime’ doesn’t apply to those or ‘physical being’ doesn’t apply to those – Suppose you thought that churchgoers went out on a Sunday night and you pointed some out and then you tried to stipulate, hey, I’m not going to call those churchgoers then. That’s not the right way of going. So I do think that, on reflection, it might be that our ordinary predicates are ……with ways to these alternative spheres in which case something like the worry that I articulated would be pressing, but I know I wasn’t being totally straight.

[new question]

Maudlin
63. [on comment by Janssen] I had a small comment that, since it came up, I need to respond. It’s this idea that I’m somehow deeply conservative and won’t ..consider? things..so me just make a quick response to this comment. The problem with …………… the theory’s telling us this and we’re just guys who hate the theory; the problem is the story you told was simply incoherent. Because what you said is …….theory…and now all I have to do is figure out how to get the macroscopic world out of it. Well, if you didn’t already know how to get the macroscopic world out of it how could you have any evidence that it was correct? Your evidence was stated in terms of stuff happening in laboratories, flashes on screens and so on; we all agree that there are interference patterns; we all agree, I take it, that there’s a wave function, have no problems with wave functions, but it just can’t be the case, it’s simply logically impossible to be the case, the position that “we have this really strong empirical evidence that this is the right theory, the only problem with it is that with the theory so far I don’t how to make sense of the macroscopic world…