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ribbleton 17-Nov-07, 10:49	Whose afraid of Possible worlds? Possible worlds exist — they are just as real as our world; Possible worlds are the same sort of things as our world — they differ in content, not in kind; Possible worlds cannot be reduced to something more basic — they are irreducible entities in their own right. "Actual" is indexical. When we distinguish our world from others by claiming that it alone is actual, we mean only that it is ours — we live here. Possible worlds are unified by the spatiotemporal interrelations of their parts; possible worlds are spatiotemporally isolated from each other. Possible worlds are causally isolated from each other How many [possible worlds] are there? In what respects do they vary, and what is common to them all? Do they obey a nontrivial law of identity of indiscernibles? Here I am at a disadvantage compared to someone who pretends as a figure of speech to believe in possible worlds, but really does not. If worlds were creatures of my imagination, I could imagine them to be any way I liked, and I could tell you all you wished to hear simply by carrying on my imaginative creation. But as I believe that there really are other worlds, I am entitled to confess that there is much about them that I do not know, and that I do not know how to find out." (David Lewis, Counterfactuals, 1973, pp. 87-88) "By what right do we call possible worlds and their inhabitants disreputable entities, unfit for philosophical services unless they can beg redemption from philosophy of language? I know of no accusation against possibles that cannot be made with equal justice against sets. Yet few philosophical consciences scruple at set theory. Sets and possibles alike make for a crowded ontology. Sets and possibles alike raise questions we have no way to answer. [...] I propose to be equally undisturbed by these equally mysterious mysteries." (David Lewis, Convention
mrvroom 18-Nov-07, 05:32	Are you saying all things are possible?
jkg20 18-Nov-07, 06:04	Let's hope not.. Hi mrvroom - ribbleton is just expounding a view about what possible worlds are, by giving us a few selected quotations from a philosopher called David Lewis. According to Lewis not everything is possible - logical contradictions for example. However, what he thought was that when something is possible, there really is a spatio-temporal universe in which that thing obtains. Sometimes that universe happens to be the actual one that you and I inhabit, in some cases it is a different causally isolated universe. Take for example the possibility that Tony Blair was never elected as PM of the UK, even though in our world, unfortunately he was. For Lewis, that possibility consists in the fact that there really is a spatio-temporal universe where a counterpart of our Tony Blair didn't become prime minister of the counterpart of the United Kingdom in that universe. Lewis has many more things to say (about 'counterparts') for example, and he devoted his career to them. However, there are other views of what possible worlds are.
jkg20 19-Nov-07, 07:26	Still waiting.... Hi ribbleton, I'm still waiting for you to explain more clearly why you think my fourfold classification of possible worlds theories (on the god's proof thread) doesn't capture Kripke's view(s) of possible worlds. Just to remind you of the classification: 1) Many worlds interpretation of QM 2) Lewisian spatio-temporal entities 3) Abstract entities 4) Purely heuristic devices - we can talk about them without having any ontological commitments about their nature (PS (1) in fact may be a species of (2), but has obvious ontological commitments that (2) needn't - specifically regarding persistence of subjects of experience) As I said, as far as I have always understood Kripke - ever since I first read him as an undergraduate - his view(s) fall(s) either into category (3) or (4), and in no case does he think of them as 'stipulations' (whatever that means). I think he may have said something like 'they're kind of stipulative' in 'Naming and Necessity', but in the context I believe what he was trying to say was simply 'it doesn't really matter what you think possible worlds are, just as long as we can all agree its sensible to talk about them' (although I think he did try to ridicule the Lewis view of them at some point, but it's been a while since I read those lectures). This could easily lead one to think he thought of them purely as heuristic devices. My feeling has always been, though, that were he to be pressed on exactly what he thought they were he'd probably go for something like 'mental constructs' which would put him into category (3). So, I await your clarification of Kripke's views: as I said, it's perfectly possible that I've misunderstood him all these years.
ribbleton 19-Nov-07, 09:43	Kripke on stipulations. One statement of clarification. Assuming we specify worlds as combinations of fundamental properties (or as combinations of larger sorts of things composed of fundamental properties), then we have what we need for de dicto modal claims. Any qualitatively described scenario is possible iff that scenario fits a possible world. But we need something more to get an analysis of de re modality. One solution is counterpart theory. S possibly Φ’s iff there is a possible world containing an individual similar to S that Φ’s, where the similarity metric is provided by context. The alternative solution I wish to consider countenances trans-world identity, saying that S is itself a constituent of many worlds, and thus S possibly Φ’s iff S Φ’s at some world. What this solution requires, however, are worlds described not merely qualitatively, but also in terms that identify the individuals of the worlds. A world that we know to contain an individual winning the election is not enough; we need to know whether that individual is Nixon or Humphrey or you or me. But how are we to determine which worlds have which individuals Different theories of modality will spell out what it is for a scenario to ‘fit’ a world in different ways. According to Kripke, there really is no problem, for we can simply stipulate which individuals are at a world. In KRIPKE'S OWN WORDS ... there seems to be no less objection to stipulating that we are speaking of certain people than there can be objection to stipulating that we are speaking of certain qualities. Advocates of the other view take speaking of certain qualities as unobjectionable. They do not say, “How do we know that this quality (in another possible world) is that of redness?” But they do find speaking of certain people objectionable. But I see no more reason to object in the one case than in the other. Kripke’s ‘stipulations’ are often misunderstood. The point is not that we somehow bring worlds or features of worlds into existence through our stipulations. Rather, such worlds must exist prior to any stipulation and by stipulating that the world contains a tall beggar, I am merely specifying which world I am talking about, viz., one in which there exists a tall beggar. Do stipulations somehow settle which worlds there are? Certainly not! We still need to justify the claim that there is, e.g., a world containing a tall beggar. But the point I take from Kripke is that if there is a world containing a tall beggar, and if there is a world in which I am a tall beggar, then just as we can stipulate that we’re talking about a world containing a tall beggar, so too can we stipulate that we’re talking about a world in which I am a tall beggar. Therefore, the epistemic problem of knowing which individual at a world is you or me or Nixon is really no problem at all.
ribbleton 19-Nov-07, 13:03	? hi jkg20 I would as an after thought to ask you to point at where in the posts do I say specifically that Kripkean stipulations couldn't be bent into those 4 categories above. These 4 categories have very fluid boundaries that's for sure. But maybe I have lost some of what you say I have written!
jkg20 20-Nov-07, 01:44	So let me refresh your memory 15/7/2007 in a post on the 'proof for god thread' entitled 'Let's be serious boys' you wrote (in reference to me and biggie and of our understanding of possible worlds theories) "neither contributor has a grasp on it because note 'possible worlds' are only stipulations". As evidence that I had a firm grasp on what possible worlds might be, I then responded with my four-fold classification of possible-world theories and pointed out that on none of them are possible worlds "only stipulations". I explicitly said that one can certainly stipulate that possible worlds exist, but that stipulating that something exists is not the same thing as having a view of what possible worlds are. I also pointed out that if you are going to use possible worlds as a lynchpin in a metaphysical argument (such as proving that god exists) you are going to have to do do more than just stipulate that they exist: you have to give an account of what possible worlds are. In reply you insinuated, in a subsquent posting entitled 'Calm down jkg20..' that I was unaware of or misunderstood Kripke's position about possible worlds. Your exact words were "I humbly suggest that the tutors you had for your doctorate should have introduced you to Kripke's view of possible worlds. Obviously the requirements for the Doctorate in Philosophy might be a lot looser than they were in my day. " Now, the only evidence you had on which to base your notion that I'd never come across Kripke and his views was the four-fold classification I gave, together with the distinction I made between stipulating something exists, and having a view as to what the nature of that thing is. Consequently, it is reasonable to assume that you then believed that in giving the classification and making the distinction, I'd missed out or misunderstood Kripke's view(s). I went on to explain exactly how Kripke's views (however interpreted) would be covered by one or other of the four categories I gave, and indicated that although he may have stipulated that they exist as part of his discourse on necessity, that wasn't the same thing as his having a view as to what possible worlds actually are. I invited you to correct my interpretation of him. Nothing you've said so far has indicated to me that there's any correction to be made. A distinction that I have always made, and perhaps you have failed to grasp then - and which could explain the mistake you made in thinking I was unaware of Kripke's work - is the distinction between what Kripke thought possible worlds were (which he said very little about) and what use Kripke made of the notion of possible worlds. The former is an issue of metaphysics, the latter more one of epistemology.
jkg20 20-Nov-07, 02:06	Kripke's 'stipulations' ...and just one more thing. In the paragraph you quote regarding Kripke's position being often misunderstood, note the initial sentence: Kripke's 'stipluations' are often misunderstood. If the scare-quoted 'stipulations' refers to anything in that sentence it refers to Kripke's stipulations that possible worlds exist, but not to possible worlds nor to Kripke's metaphysical view of what possible worlds are. You may have misread it to think that you could simply substitute 'stipulations' with 'possible worlds' and retain the sense of the sentence. However, the sentence: Kripke's 'possible worlds' are often misunderstood is clearly not the sentence the author goes on to explain. That substituted sentence invites a complete misunderstanding of Kripke, since it would invite conflation of the metaphysical and epistemological issues I just distinguished, and which Kripke himself also clearly kept apart. This simple substitution, though, may account for why you originally thought I'd misunderstood Kripke, and why you originally said 'possible worlds are just stipulations'.
ribbleton 20-Nov-07, 04:47	Kripke Well you jumped (maybe naturally) to many deniable conclusions from those brief bare posts of mine. Note contrast the contrast I am suggesting between the likes of Lewis, Stalnaker and Kripke The former two argue that possible worlds are a set of possible individuals with Lewis arguing that we cannot make adequate sense of the notion of possible worlds unless we actually accept that they are real. While Kripke on all natural interpretation of what he says clearly hints that possible worlds are merely sets of sentences or as constructions out of the inhabitants of the actual world. But more than ‘hints’ he says in disagreement with these others that possible worlds are STIPULATED rather than discovered. That’s why he makes no direct comment on what they actually are. For him they do not have to be out there in some spatial temporal sense for them to be usefully employed for the problem of modality, modal logic, counterfactuals propositions and properties. I think this is uncontroversial and I shall be sticking to my guns on this interpretation of Kripke’s views of possible worlds. We will have to agree to disagree in the final analysis.
jkg20 20-Nov-07, 07:01	We have no disagreement over Kripke then ...as I said, he falls either into category (4) - possible worlds are merely heuristic devices - or (more likely) into category (2) as abstract entities (sets of sentences/mental constructs). The difference between either of those views and Lewis's is, and always has been, clear.
jkg20 21-Nov-07, 01:09	Helping yourself to possible worlds Depending what you want to do with 'possible worlds' you either owe a full account of what they are, or you don't. If you are trying to uncover some of our intuitions about necessity, contingency and reference, arguably you don't need to say too much about them, you just need to give them an intial gloss so that people have an idea of what is being talked about. That's why Kripke's arguments in 'Naming and Necessity' are not (at least not prima facie) undermined by the fact that he says very little about what possible worlds are. However, you might have more ambitious aims. David Lewis, for example, attempts to account for the truth of many different kinds of statements in terms of possible worlds (e.g. statements about properties, natural kinds, causation, counterfactual possibilities, the list goes on). As he is dealing with metaphysical concerns, rather than just our intuitions about certain concepts, an account is owed of what possible worlds actually are. Of course, Lewis gives such an account. Were someone to attempt to use the notion of possible worlds in presenting an argument that god exists, and this has been tried, we would certainly need to hear more about what possible worlds are. He should not just stipulate that they exist.
ribbleton 21-Nov-07, 09:43	Possible worlds All I take possible worlds to be is the matter of 'what might have been'. That's all I am going to stipulate.
jkg20 22-Nov-07, 02:20	In which case... ..you won't be able to use them in an argument to establish any metaphysical conclusions about what there is, since your opponent could attack the argument for the conclusion on the bases that a proper understanding of what possible worlds actually are entails that the conclusion is false. And with that, I think we've brought this circle of discussion to close.
ribbleton 22-Nov-07, 05:54	Its only just beginning. A lot can be gained from proving that a universe with a God would be scientifically different from a universe without God. Even if either universe only might have been.
jkg20 22-Nov-07, 08:06	Well... ...it depends what you mean by 'scientifically different'. If you mean something like 'verifiably empirically different' then indeed it would be interesting to establish a proof that a universe with God would be scientifically different from one without God, since then we'd be able to empirically establish whether he exists or not in this one. Furthermore, in that argument you may be able to help yourself to the notion of possible worlds, since all you would be establishing is the possible existence of a piece of evidence of a certain kind. The interest of the argument would lie in the kind of scientific evidence you think would swing the question of God's existence, not (at least in the first instance) anything about the nature of possible worlds. Although such an argument itself wouldn't prove that God exists, it is still an argument that would have a place on the 'proof of god thread'. On the other hand, you may mean something entirely different by 'scientifically different' - it seems I often misinterpret your words.
ribbleton 22-Nov-07, 10:09	The Sleeping Beauty problem On Sunday, Beauty is put to sleep. She is awakened once on Monday, and put to sleep again after being administered a memory-erasing drug that causes her to forget her awakening. A fair coin is tossed. If and only if the coin falls tails, Beauty is awakened again on Tuesday. She knows all this. When she awakes on Monday, what should her credence be that the coin will fall heads? The Sleeping Beauty problem is a variation of some very similar problems of “imperfect recall” that have been discussed for some time in the game theoretic literature.Sleeping Beauty is an example of a problem involving self-locating beliefs, i.e., beliefs that an agent, or a temporal part of an agent, might have about its own location. An agent-part that knew exactly which possible world is actual can still be ignorant about its own location in that world. That can happen if the world contains two or more agent-parts whose evidential states are subjectively indistinguishable. These agent-parts would then be unable to determine with certainty their own spatiotemporal location. Beauty knew that the outcome of the coin toss would be tails, she could not know whether it was currently Monday or Tuesday.) Another way of expressing this is by saying that the agent-parts would be ignorant about which centered possible world they are in even though they know which possible world they are in. Yet another formulation is that agent-parts, or “observer-moments”, possess all non-indexical information about the world but lack some indexical information. Here we shall use these expressions interchangeably. The Sleeping Beauty problem is but one piece of the larger puzzle of how to relate indexical to non-indexical information in our reasoning.

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