Friday, 30 September 2016

Feedback please: Thesis draft, Necessity and Propositions

Here is a draft of my PhD thesis (updated 29 OctNecessity and Propositions. It contains my best treatments so far of some of the topics covered on this blog over the last five or so years. I have a bit more polishing to do and will be handing it in around mid-October. I still have a chance to make substantive changes, so please give me any feedback you can, substantive or otherwise! (Either comment here, or email me at 'tristan8haze@gmail.com' without the numeral.)

As I make final changes I will keep re-uploading it to the same location.

9 comments:

  1. Hi Tristan,

    Congratulations on your thesis.
    I haven't gotten to your theory yet - I'm reading chapter 3 -, but so far, it's very interesting.
    Regarding chapter 3, I think the following is a potential (minor) difficulty:

    You seem to be to some extent confident that the actual world contains no talking donkeys, etc.
    I'm not entirely sure those things are possible, though, so I'm not sure the modal realist' reply fails.
    Would something that talks still be a donkey, in the usual sense of the words?
    The same applies to your counterpart who says "hello" for so long; how would he be "just like you"?

    However, assuming that those things are indeed possible, wouldn't your assessment that they do not actually exist commit you to the view that either there are no parts, regions, etc., of the actual world causally disconnected from us (a bold claim), or else we have sometimes knowledge (at least make good intuitive probabilistic assessments) about the goings on a causally disconnected part, region, etc., of the actual world, since we know they do not contain talking donkeys and the like?

    That seems to me problematic in light of the natural candidate you propose in this context, and specifically the view that causal acquaintance is required for knowledge of the concrete.

    Moreover, the following specific issues might be raised in this context.

    1. If the universe has infinitely many planets, etc., and if Quantum Mechanics is at least as good an approximation as it seems to be, many absurd or ridiculous possibilities are actual. Even if the universe is finite but big enough, absurdities would abound. That may well include your examples, at least depending on how one construes "like me" and "donkey".
    Personally, I don't know there are any good arguments against an infinite (or sufficiently large) universe based on present-day physics, or any other empirical finding. Maybe you can say that the causal acquaintance is of a different sort, but it's a difficult matter.

    2. If there is a multiverse of the sort proposed by some physicists, even weirder things are actual. While (I tentatively guess) there might be some good reasons to reject them based on present-day physics, I don't know whether your assessment was based on them; rather, it seems to me it was not based on that, but an intuitive probabilistic assessment, using either no causual acquaintaince or only causal acquaintance with the things we are in fact familiar with. I don't have an objection to that kind of assessment, but it seems to me it undermines the "natural candidate" above.

    On the other hand, your objections to Lewis's reply that the boundary is given by whether something is necessary or contingent (in particular, cases of necessities a posteriori) look decisive to me.

    ReplyDelete
    Replies
    1. Thanks very much for the comments!

      'You seem to be to some extent confident that the actual world contains no talking donkeys, etc.' - The rhetorically relevant point is that I don't think *reality as a whole* contains such things. Lewis would happily agree that the actual world probably doesn't.

      'The same applies to your counterpart who says "hello" for so long; how would he be "just like you"?' - The point remains that, whether it's me or not, I have a strong feeling that reality as a whole contains no such thing.

      'wouldn't your assessment that they do not actually exist commit you to the view that either there are no parts, regions, etc., of the actual world causally disconnected from us (a bold claim)' - Again, the relevant point is that it seems plausible that they don't exist (as Lewis would grant that they don't *actually* exist). Lewis seems to be committed to the thesis you speak of, since according to him two things are worldmates iff they are spatiotemporally connected (or something analogous if the world in question isn't spatiotemporal), but I see no reason why I would be committed to it.

      '1. If the universe has infinitely many planets, etc., and if Quantum Mechanics is at least as good an approximation as it seems to be, many absurd or ridiculous possibilities are actual.' - Fair enough. I wouldn't want to rest too much of my case against modal realism on there not being things like talking donkeys anywhere in reality. It's just one intuitive consideration which seems to me to be a (defeasible) mark against modal realism.

      'your objections to Lewis's reply that the boundary is given by whether something is necessary or contingent (in particular, cases of necessities a posteriori) look decisive to me' - Thanks! That seems to be one of the sharper original points in the chapter, so I might try to make more of it some day.

      Delete
    2. You're welcome, and thanks for your reply too.

      "The rhetorically relevant point is that I don't think [b]*reality as a whole*[/b] contains such things."

      I get that's the point that you were making. I wanted to make a different point and reckoned that if you think reality as a whole doesn't contain such things, you don't think that the actual world does (if you accept worlds). But "reality as a whole" also works for my point, so I'll leave aside the actual world.

      "Again, the relevant point is that it seems plausible that they don't exist (as Lewis would grant that they don't *actually* exist). Lewis seems to be committed to the thesis you speak of, since according to him two things are worldmates iff they are spatiotemporally connected (or something analogous if the world in question isn't spatiotemporal), but I see no reason why I would be committed to it. "
      I don't know that he is so committed. Isn't it compatible with his modal realism that (say) there are things in the universe beyond our light cone which are causally disconnected from us, but are part of the same spatiotemporal whole?

      In any case, my point wasn't that you'd be committed to the view that there are no parts, regions, etc., of the actual world causally disconnected from us period, but rather, to the view that either there are no such parts, etc., or we have sometimes knowledge about the goings on a causally disconnected part, etc., of the actual world (or reality as a whole), since we know if they exist, they don't contain talking donkeys, etc. (at least, we properly assess that such things probably don't exist).

      "I wouldn't want to rest too much of my case against modal realism on there not being things like talking donkeys anywhere in reality. It's just one intuitive consideration which seems to me to be a (defeasible) mark against modal realism. "
      I agree it is. In fact, I'd say we certainly don't know that there are talking donkeys, either. As you put it later, modal realism is at bottom crazy speculation. Assigning it a high probability doesn't seem epistemically rational to me: the prior seems extremely low (even if there are talking donkeys; modal realism combined with standard possibility assessments implies that there are many other things), and I just don't see any consideration that raises the probability beyond "too improbable".

      That aside, my point was that that particular consideration - while good against modal realism - seems to undermine the suggestion you make later about our lack of knowledge of the goings on in regions we have no causal acquaintaince with. If it's true that we know something about what happens in the actual world/reality as a whole, even if we happened to have no causal acquaintance with some parts of it, then the natural way to draw the line (about when we need causal acquaintance) isn't correct: sometimes we don't need causal acquaintance to get knowledge about concreta (at least, about what concrete things don't exist, but that seems enough).

      I mentioned an infinite universe, QM, etc., as a way to further motivate my point, but leaving that aside, I think that the denial of talking donkeys, etc., in reality as a whole commits you to the view that either there is nothing in concrete reality as a whole we have no causal acquaintance with, or else we do know something about the goings on in concrete regions/universes/whatever with which we have no causal acquaintance: namely, we know that there are no talking donkeys, etc.

      By the way, apart from your objection to Lewis's way of drawing the line, I think the semantic objection, and the contingent totality objection (in particular your example "If I had behaved differently this morning...") are also very strong objections to Lewis's modal realism.

      Delete
    3. 'That aside, my point was that that particular consideration - while good against modal realism - seems to undermine the suggestion you make later about our lack of knowledge of the goings on in regions we have no causal acquaintaince with.' - Ah, I see what you mean. I will think about it.

      One thing I will say is that maybe you can object to a theory which, together with plausible assumptions about the extent of (the relevant kind of) possibility, implies the existence of certain things which it seems absurd to suppose reality contains, without claiming to have *knowledge* one way or the other about such matters.

      By the way I just re-uploaded the thesis, so if you plan on reading on with the later chapters, it's worth re-downloading it.

      Delete
    4. A further thought: even if I were to say that we do 'know' in some sense that certain absurd things do not occur in reality, that not a *lot* of knowledge. It is a far cry from knowing that all sorts of specific things (possibilities) *do* occur, as modal realism, together with the assumption that we know there are such possibilities, would suggest.

      Delete
    5. "One thing I will say is that maybe you can object to a theory which, together with plausible assumptions about the extent of (the relevant kind of) possibility, implies the existence of certain things which it seems absurd to suppose reality contains, without claiming to have *knowledge* one way or the other about such matters."
      Maybe you can, but I get the feeling that "absurd" in this context implies that it's extremely improbable that all of those things (at least together) exist (i.e., that that's a proper probabilistic assessment based on the available info), and it seems to me it would be difficult to go on to deny that there is knowledge once one accepts one can make proper probabilistic assessments like that.

      "A further thought: even if I were to say that we do 'know' in some sense that certain absurd things do not occur in reality, that not a *lot* of knowledge. It is a far cry from knowing that all sorts of specific things (possibilities) *do* occur, as modal realism, together with the assumption that we know there are such possibilities, would suggest."
      I think that's a good point. The fact remains that modal realism still has wild implications (under usual possibility assessments) about what's happening in all sorts of universes, planets, etc., without a shred of evidence for it beyond some analysis of our modal talk that doesn't seem to reflect how we use the words, anyway.

      "By the way I just re-uploaded the thesis, so if you plan on reading on with the later chapters, it's worth re-downloading it."
      Thanks; I just downloaded it. The chapters I've yet to read are 5, 6 and 7. I look forward to reading them.

      Delete
  2. I just read your account on chapter 5, and so far, it seems very plausible to me. It will take me quite some time to digest it, though, so this is only a preliminary impression, but so far, so good - and it if it holds, it looks like an important contribution to me. Congratulations.

    ReplyDelete
  3. Your account of propositions, internal and external meaning also seems like a plausible to me, so congrats again.
    I'm still not sure about how the concept of "meaning-radical" works, but in any event that's not required for the main part of your take on meaning, but only for the part on analyticity, and you say that's an issue for further research, so that's not a worry about your account.

    By the way, while a secondary issue, I'm thinking there are alternatives to XYZ that might block (at least partially) the scientific worry that you mention (in re: Twin Earth), like:

    a. Instead of XYZ, we may consider Twin cats, which look (from the outside) and behave like cats, but have very different DNA. While that's not certainly physically possible, it may well be so (it looks a lot more likely to me than XYZ and water). Moreover, we only need that they look and behave the same when it comes to behavior Twin Earthers have ever observed (we can switch from cats to something less common, to make it more probable), which increases the likelihood that it's physically possible. Maybe opposite chirality DNA will do (though in that particular case, there is also the issue as to whether they're cats).

    b. Instead of Twin Earth, one may posit Anti Earth, in a galaxy made of antimatter. There is anti-water instead of water (and anti cats, etc.). But the internal meaning of "water" is the same. That's also not certainly physically possible as far as I know, but it may well be so, even in a universe with the same laws as ours, and even if antimatter is infrequent (one can just posit a sufficiently big universe).

    c. One may posit Simulated Earth - examples abount in fiction -, where Simulated Oscar lives in a simulation.

    But then again, I think your response takes care of the worry nicely, without having to worry about whether it's physically possible.

    A detail:

    On page 17, chapter 6, it should say "Alexander" instead of "Plato".

    ReplyDelete
  4. Thanks very much indeed, this is very encouraging. Thanks also for the thoughtful comments and catching the Alexander/Plato mistake.

    ReplyDelete