There Are No Possible Worlds

I raise some objections to the view that modal facts are grounded in facts about possible worlds.
0:00 - possible worlds
2:49 - irrelevance
7:04 - epistemic access
11:35 - maximality and models

[@KaneB]

There are no modal facts: kzbin.info/www/bejne/fF7IhJRvgLeCndE But if there were modal facts, they would not be facts about possible worlds.

[@kazz970]

Other possible worlds were harmed in the making of this video.

[@KaneB]

Nelson Badman, "Ways of World-destroying"

[@benzur3503]

@@KaneBI am become Saul Kripke, destroyer of worlds

[@norabelrose198]

To strengthen your case: in social science and computer science people usually use Pearlian counterfactuals, which are based on causal models, and don’t require talking about possible worlds at all.

[@1shotcountz]

What a distressing title lol

[@monkiplatts9224]

I want the ability to go into galactic schizo rants like him

[@uninspired3583]

Is there something that separates possible worlds and plain old imagination?

[@mf_hume]

Great video. Thanks, Kane!

[@justus4684]

Sir, this is a Walmart...

[@thomasjdk]

Sir, this is a stripclub

[@hss12661]

Haha

[@uotrbvelepr8018]

Sir, I am David Lewis

[@uninspired3583]

Possibly..

[@panta_rhei.26]

​@@uninspired3583😂😂👏

[@jmike2039]

2:15 great clarification here. This is how I have tended to view possible world semantics, as the whole possible worlds thing was off putting me getting into philosophy, especially David Lewis's view. I think most people are super confused when introduced to this concept, and ive found that when talking to people who dont read any philosophy a more accesible concept they are probably familair with is 'in a perfect world i would have X'. From there you can strip it down to just what you 'could have done or could do' etc and better express that you are just trying to use it as a heuristical device.

[@rebeccar25]

No

[@jmike2039]

@@rebeccar25 quit playing games with my heart

[@humeanrgmnt7367]

Excellent. TY!

[@MyriadColorsCM]

About epistmeic access, I believe this objection is an inversion of the proper metaphilosophical hierarchy between metaphysics and epistemology: it is metaphysics which grounds epistemology, not the other way around, we cannot say that a certain metaphysical claim is true or false based on whether we can KNOW if such a claim is true or not, because of the simple fact that we can only know what IS and not of what IS NOT, As such, questioning a platonist by positing he cannot know of abstract entities is moot, for if abstract entities exists, then we have some sort of access to them, and it is incumbent on the platonist to give an account of epistemology based on the metaphysics he assumes as true. The question is: if platonism is true, then how can we have access to abstract entities WITHIN a platonistic metaphysical framework, you must take it to be true and an hypothesis and think on how a platonistic epistemology might work, but if you can only accept empiricism, then you accept a set of metaphysical assumptions which cannot be reconciled to platonism. As such the objection would be moot to a platonism, because to him, empiricism itself would be false as an epistemology. And if you wish to object to platonism, you must object to its metaphysics, not to its epistemology.

[@KaneB]

>> if abstract entities exist, then we have some sort of access to them Why? I'm not sure even most platonists would commit to that. It's one thing to say that, in fact, we do have access to the facts about these abstract entities. It would be quite another to say that there is something about abstract entities that guarantees we have access to facts about them. That doesn't seem to be true even of concrete entities. >> The question is: if platonism is true, then how can we have access to abstract entities WITHIN a platonistic metaphysical framework I agree, but this seems to me to be exactly how the epistemic problem is usually presented. We assume, for the sake of argument, the platonist's metaphysics. Then we show that there is no way, given that metaphysics, for us to access the facts about abstract entities. The immediate conclusion is not that platonism is false, but that the platonist cannot by their own lights give an adequate account of our knowledge of the relevant domain.

[@Ivan.Wright]

Could be that "movement through time" is itself movement through worlds (or states), each moment being analogous to a static frame in a larger matrix of possibilities. Distance between any two frames would be defined by minimal dissimilarity or smallest relative deviation from local norm. Probability would be defined by the energy it takes for the system to change from one state to another with high probabilities requiring lower change. In the case of talking about alternative realities we would be talking about locations in the matrix relative to our own where the energy required to change to that state exceeds what's available while from another state the energy required is available. The difference between these two states would be the difference in change between a shared probably and the energy required to change from that state to the local and supposed realities. That's at least my attempt at expressing a portion of the hypothetical dynamics as I understand them.

[@GhERM2SOIED72]

Well said!

[@dicktrolington416]

Isn't that kind of how temporal logic works?

[@disassembledpurity]

this is so useless bro, none of this word juggling can ever be properly verified in any way, no point in even thinking about this nonsense

[@Ivan.Wright]

@@disassembledpurity Not with that attitude. Try again

[@disassembledpurity]

@@Ivan.Wright what?

[@whycantiremainanonymous8091]

One of my big pet peeves! I can't stand that "possible worlds" talk (back in the day I sometimes bothered speakers at a local philosophy department colloquium with questions about what possible worlds are they talking about, and where do I find some...) I actually think that even the use of possible worlds as a technical convention is unhelpful. First, because nobody would take the idea of metaphysically real possible worlds seriously in the first place without it. Secondly, because it facilitates a lazy habit of mind (and God knows Analytic philosophers can be lazy; just look at how much the same couple of made-up examples are regurgitated in discussions again and again, and again, and then some more...). Lastly, and most importantly, because philosophers often tend to make the basic mistake of thinking about the actual world as if it were merely possible. There's no reaon to play into that unfortunate tendency, instead of resisting it.

[@KaneB]

Yeah, "Kripke semantics" or "frame semantics" would be less misleading, I think. When we give a Kripke model , we need not interpret the elements of W as being worlds in any literal sense. Indeed, interpreting them this way isn't particularly useful if we're using Kripke semantics to model other logics - in the case of temporal logics, for instance, it's better to think of the elements of W as times rather than the worlds. So I'm inclined to agree that even as a technical notion in model theory, we might be better off without "possible worlds". On the other hand, this is somewhat outside my area of expertise, and I wouldn't be surprised if it's only metaphysicians who are inclined to reify these formal abstractions.

[@ataraxia7439]

How do you think would play into questions that are “what if X necessarily impossible thing were true?”. For example I can imagine “if a mathematician who studies geometry was show an true square circle” “he would probably be in awe at seeing something impossible and would probably try to understand what he’s looking at”. I don’t think there’s any possible world with a square circle but I think you can still say true or false things about what impact it could have.

[@KommentarSpaltenKrieger]

Thanks, this is exactly the problem I see with possible worlds talk: To say that only one condition can be changed and the rest remains constant is an assumption that, more often than not, seems false. Even if I intend to have only one fact be different (let's say that Nixon doesn't become US president), for this one fact to be different, there must, arguably, some prior fact be different, too, especially if, as talk about the "closest possible world" heavily suggerst, we must assume the same basic causal principles in that other world, too - and hence work with the assumption, that (at least on the larger scales than the quantum level) "ex nihilo nihil fit".

[@neoepicurean3772]

Have you ever looked into Wittgenstein's metaphysics in the Tractatus? I think it implies a form of modal realism. I haven't researched this yet, but I was just wondering if you'd thought about it. *After a quick look into it, it seems the Tractatus puts forth a view known as 'combinatorialism', which doesn't imply any modal realism. But it would seem to have some problems. So please make a video on combinatorialism next :D

[@DigitalGnosis]

You still need weird entities called propositions (or sachverhalten) that exist in some weird way and can be recombined in weird ways. Seems spooky, confused and unnecessary. PI Wittgenstein is much better on this!

[@neoepicurean3772]

@@DigitalGnosis Is there any stuff about this 'combinatorial' view in PI? Haven't got that far yet.

[@KaneB]

Combinatorialism can be a kind of modal realism, and this is probably the most straightforward form of the theory -- it's not Lewisian concrete realism, of course, but it's realist in the sense that it postulates possible worlds as kinds of abstract objects, say, set-theoretic constructions from distributions of matter. These set-theoretic recombinations of matter are not mere formal tools or stories or conceptualisations: they exist objectively, and ground objective modal facts. That is, actual particulars and universals exist, and the set-theoretic recombinations of those particulars and universals also exist. I don't remember the Tractatus well enough to say what, if anything, Tractatus-Wittgenstein said about this matter. Tractatus-Wittgenstein was at least realist about the basic ingredients of combinatorial worlds: namely, actual particulars and universals.

[@KaneB]

@@DigitalGnosis PI Wittgenstein sucks, but "propositions" is probably the worst idea in analytic philosophy.

[@neoepicurean3772]

@@KaneB Thanks! Great stuff. Make a video on this when you have time! (If you haven't already, haven't found it if you have).

[@italogiardina8183]

Dreams seem to do the job given being a dream is real but from being awake that dream was maybe possible if coherent with Particle physics that also has dream like properties for actual real world observers by token of verification of virtual particles from the field that through collision in a collider produces observables, as for example the Higgs Boson. So observation seems to imply real virtual particles. This then implies the many worlds interpretation that has the logic of possible worlds.

[@DigitalGnosis]

Im just starting the video (1:45 timestamp) so Im assuming you're going to end up making some of the same points, notice what actually happens when you are clarifying for the listener how to use "possible world semantics"... "*Imagine* everything happens the same up to the point I drop the glass...". All that's happening is that as philosophers we're training people to use words in a certain way and part of that procedure involves imagining in a certain way - no magic metaphysics needed - it all takes place in front of your eyes!

[@DigitalGnosis]

Glassy essences and what not

[@KaneB]

I don't propose any positive account of possible worlds here. But yes, this is pretty much how I think of them: a possible world is just a story that we tell, where we imagine that things go differently. Of course, treating possible worlds this way completely empties them of any substantive metaphysical consequences. Indeed, describing these as "possible worlds" is something of a misnomer, since there won't be any substantive distinction between the possible and the impossible worlds. I can tell a story in which there are round squares, or in which 1+1=3, or in which there is a box that is both occupied and empty.

[@DigitalGnosis]

@@KaneB We are in agreement. I actually think it was your video years ago on the Lewis Caroll Achilles and the Hare paper that first got me thinking this way.

[@saimbhat6243]

Lol, My first reaction to kripke's shenanigans and modal logic was a good cynic laughter and i am proud that it has remained same so far. "Modal logic" is the epitome of "Well, actually...." geekiness.

[@badabing3391]

something similar to this reasoning is why i wonder if criticizing the problems of historical, or even modern events is worthwhile or not. Would anything being done any better not imply a completely different type of world in which that history occured in? Maybe a lot of cases are not of that form, but i wonder if most of the cases we think are criticizable are of that form, and if we could ever find out. Apologies if my vocabulary isnt strong enough to prevent ambiguity, im really tired lol.

[@howtoappearincompletely9739]

I'm with you on this. Talk of "possible worlds" is a mere façon de parler, a dubious "aid" to understanding (actually an aid to formal logical expression). Re counterfactual claims in science, if one is a determinist (hard determinist, superdeterminist, or whatever qualification is needed), aren't *all* counterfactual claims fictions?

[@writerightmathnation9481]

At 18:01, you said that it’s not clear how we assess closeness or similarity, but the possible world semantics uses models as in model theory, i.e. relational (or relational/functional, etc) structures (see, e.g. the text by Bell & Slomson, or by Chang & Keisler, or by Bell & Machover), and this models (structures), together with selected morphisms, form categories (in the category theoretic sense) so that some Grothendiek metrics or similar kinds of metrics (a functions) can be defined, provided various kinds of (dis)similarity measures that can be ported over to the syntactic side by associating each structure A with its complete theory, Th(A), each of which is a maximal consistent set of sentences. Now, at 18:22, you mention “scientific models”, and unfortunately this constitutes a conflation of notions. In the logic course that I designed where I teach mathematics, I use s textbook called The Logic of Thermostatistical Physics, by Emch & Liu, which explores the conflation aspects of this historically misused terminology and helps students (readers) to de-conflate them. Roughly, what is often called a “mathematical model” in scientific discourse is actually a list of sentences in a mathematical languages, so it’s not a structure but is more like an axiom system. This is a major reason that that abused terminology refers to an incomplete description. That being said, I’m not exactly objecting to your concerns about the use of possible worlds semantics (Kripke semantics) to ground metaphysics of modal reasoning, especially since you provided the caveat that you don’t object to possible worlds semantics to provide a model theory for modal logic.

[@GhERM2SOIED72]

Saying how things might have been different (and ARE different) in another possible world is a method for examining parts of the current world. If something is true in all possible worlds, then, yes, it is a fundamental part of existence.

[@GhERM2SOIED72]

There is no difference between the thought and the thing.

[@GhERM2SOIED72]

Infinitely many worlds are not "complete".

[@GhERM2SOIED72]

For water to be gaseous you need to clarify which water. If you are talking about H20, then a lot of things would have to change- if you wanted biological development to be similar you'd probably be dealing with an incomplete world. You'd also need to rethink a lot about molecular physics to make this work, unless you want to end up in an incomplete world.

[@Alex.G.Harper]

*the irrelevance objection:* what does that have to do with me? well, you and i are actually existing, and you could be continuous with some better or worse possible you. our actual world could be what is of some possible world. in some possible world, i die early of smoking. i, actually existing in this world, if i keep on smoking, will become actually existing as continuous with the person who kept on smoking and died. this actual world could be continuous with some possible world that would become the actual world. this is a slightly different view than lewis, but it still includes possible worlds.

[@saintsword23]

A proper understanding of nominalism just cuts through these issues like butter. These issues only come up because people are really uncomfortable separating their ideas about the world from the truth of the world...separating phenomena and noumena.

[@stevenmason4150]

Models can be grounded by a weak naturalism, say, (Lewis's) 'Human supervenience', I guess. On the other hand, it can be said that dispositions (observable under scientific trial) are, in any case, irreducible to counterfactuals, i.e. C B Martins 'fink' counterexample. That matters because it suggests that our intuitions about possible worlds are not maximally compete, as you say.

[@stevenmason4150]

Typo, read 'Humean' supervenience...

[@wenaolong]

But what of the temporal tense of possibility? It is easier to speak of possibility as a mere cognitive construct for modal reasoning about the present and past, but what of the future? Since there is no future which is yet actualized, and many varieties of actualization are possible, none of them are actual. Yet surely one of them will come to exist, though it doesn't yet. All past possible worlds that do not lead to the present can be seen as cognitive devices, and all variations of the present which would result from them inherit that "abstraction". But the futurity of the present is yet to be. But it most certainly will happen. How it will happen may yet to be known by us, but it will happen in some way or other which will be a modification of the actual present world. The same cognitive devices of modal reasoning will apply to that analysis, but it will be in consideration of a very real world that is to manifest (albeit as a branch of this actual world). Although future possible worlds may be seen as modifications of the present actual world rather than worlds in themselves, they nevertheless do not exist now, and yet will exist. This could have many ways of being elucidated and deconstructed but it seems an interesting way to look at possible worlds as ontologically substantial.

[@DaKoopaKing]

There's some dude that was on Majesty of Reason's channel who buys into modal talk but argues that all future contingents are false. I don't remember what his main points were but you might be interested in that.

[@G_Doggy_Jr]

Response to the "irrelevance" objection: We appeal to counterparts all the time. If your neighbour is burgled, you think, "holy crap, that could have been me!" But, why does what happened to your neighbour "over there" say anything about what _could have_ happened to you? Because you resemble your neighbour in relevant respects. Like your neighbour, you store valuable objects in your home, and you do not have a security system installed. It was just a matter of chance that they got robbed and you didn't. So, we ordinarily take things that happen "over there" to _represent_ what might happen "over here". At this point, it seems if you want to use the "irrelevance" objection, you have two options. Either you can reject this type of inference altogether, or you can endorse appealing to this-worldly counterparts to ground modal facts, while rejecting any appeal to other-worldly counterparts. Now, in your discussion about why you believe you "could have worn a blue shirt", you appeal to your counterparts when you say that "people like me wear blue shirts". Thus, it seems that your "irrelevance" objection needs to allow this-worldly counterparts to represent this-worldly possibilities, while rejecting this relation for other-worldly counterparts.

[@noah5291]

Possible worlds being a material reality is a religion.

[@ovrava]

No, because there are good arguments for them.

[@martinbennett2228]

Is your argument an a priori case against the concept of free will? The concept of free will depends on the possibility of an alternative world in which it was possible to have done otherwise. About water, although its physical properties could be expressed as you do for illustrative purposes such as to a class of students, more generally a description would not involve conditional modes, but simply be an account of the contribution of the enthalpy of hydrogen bonding to the enthalpy of vaporisation. More generally I think any positive statement can be expressed as a negative conditional: 'If it did not have property x, then ...'

[@KaneB]

We might think that free will requires the possibility to do otherwise - so a necessary condition of my freely choosing to perform action A is that I could have chosen not-A - but this doesn't commit us to believing that there is an alternative possible world in which I or one of my counterparts chooses not-A. I deny that modal truths are grounded in facts about possible worlds. "I could have chosen not-A", "it was possible that I chose not-A" can be true, even if there are no possible worlds. More strongly: possible worlds, as most philosophers think of them, are just irrelevant to these sorts of modal claims. As for the case of counterfactuals in science, the question is what makes that negative conditional true. "If it did not have property X, then..." Then what? Maximal states of affairs seem irrelevant here. What is the closest possible world in which water does not have intermolecular hydrogen bonding? I don't think there's any fact of the matter here; or if there is some fact of the matter, it will just be irrelevant. Now perhaps we think that we should take some attitude other than belief to such counterfactuals, in which case I'd agree that there is no direct problem here for the possible worlds theorist. But then this raises the question of why we should ever believe any counterfactual. If counterfactuals are not believed, then one important motivation for introducing possible worlds is undermined.

[@MrAwesomeTheAwesome]

If your interpretation of free will requires a possible alternative world in which you have done something different, yes. I think that interpretation of free will is deeply flawed for other reasons as well. Imagine the world is non-deterministic, and therefore enables this interpretation of free will to be valid - then the impetus for the different decisions being made is entirely random. Not at all caused by the personality or decision-making abilities of the individual. I doubt any would argue that allowing dice rolls to influence your decisions qualifies as 'free will'. Under a compatibilist lens, however, we consider the deterministic sequence of our thoughts and opinions leading to our actions to constitute free will. (With free will being infringed upon when the individual's beliefs and desires bear little impact on that individual's actions - such as under threat or coercion). Using that definition of free will, assuming there is exactly one possible universe (the one you're living in and experiencing), you have free will. I strongly prefer this definition of free will because it A) meshes well with the colloquial usage of the term (even if it defies a common colloquial belief about free will - that one must possibly have been able to do other than they did), B) has meaningful implications on morality and consequence, and C) actually makes any sense. My last reason is a little tongue-in-cheek, but I do consider definitions of free will which rely on non-determinism rather silly, since they essentially boil down to arguing that introducing real physics-level randomness into our actions constitutes free will. If there are *no* possible universes at all *including* this one, then you don't have free will because nothing exists.

[@martinbennett2228]

@@KaneB I do not understand how your "I could have chosen not-A..." is any different from 'I could have dropped the glass'. It is a bit hard for me to argue the requirements for free will because even aside from the alternative world question I find the concept of free will to be intrinsically incoherent. As for counterfactuals in general, you make some good points. It is clear to me that counterfactuals can only make sense within prescribed (and agreed) rules. Once we are within the rules counterfactuals make sense and are actually inevitable, we do it all the time: supposing you intend to buy a new phone, you might look at the characteristics of alternative phones and try to compare counterfactual futures with them. Understanding of the limitations of counterfactual alternative worlds will help you understand how error prone these assessments tend to be.

[@realmless4193]

The biggest problem with this argument is that it fails to adress the primary reason why this theory exists and because of that brings up largely irrelevant points. People believe that possible worlds are things worth talking about because they are certain that they have free will, specifically opt-ability. Possible worlds is a convenient way of explaining the modal consequences of believing in free will. It is also a natural consequence of believing in the existence of any other engine of potentiality such as randomness. Possible worlds are relevant because we analyze potentialities constantly in order to make decisions. They are episemically accessible to the degree that we are aware of the various ways in which real things could have changed or erged. Our knowledge of possible worlds is imperfect just as our knowledge of the real world and our knowledge of both increases as we learn more about what is real. Possible worlds may be maximal and just as complex as the real one, but there is never any need to anslyze the whole of a particular possible world, just commanalities between them to analyze modality.

[@quippits3201]

If there's all these possible worlds but only one real one, then how do we know we're in the real one? 🤔Something to think about

[@rebeccar25]

I’ve never noticed Kane B’s eyebrows before this video.

[@KaneB]

I can't believe you've never noticed my beautiful eyebrows before!

[@rebeccar25]

@@thotslayer9914 who

[@mrbwatson8081]

Models of reality are like a maps they are NOT the territory.

[@bigol7169]

Do possible worlds assume indeterminism? Doesn’t ‘I could’ve worn a blue shirt’ imply that the atoms in the universe could’ve bumped into eachother differently? ‘I could’ve chosen to wear a blue shirt’ also assumes something similar about your brain state, and may even assume free will. I have no historical knowledge of the possible worlds movement in metaphysics, but I wouldn’t be surprised if it came from Schrodinger and the quantum revolution

[@KaneB]

No. Suppose our world is deterministic. Even so, it might be possible for there to be indeterminism, or for there to be different initial conditions. In which case, on the view that modal facts are grounded in facts about possible worlds, there is some world that is indeterministic, and there is some world that has different initial conditions. Even if our world is deterministic, "I could have worn a blue shirt" might still be true because there could be some world with different initial conditions in which a counterpart of me does wear a blue shirt. Possible worlds semantics in modal logic and metaphysics doesn't have anything to do with quantum mechanics. Talk of possible worlds in philosophy predates that actually, though it didn't become so popular until the mid-20th century.

[@wenaolong]

Reflection on how things could have been different may not affect the past, but even observation of things as they "actually are" may alter how they "actually are".

[@benzur3503]

Quite the opposite. They assume determinism. They have very little if anything at all to do with quantum mechanics and statistical potentiality of physical events occurring. Possible worlds are distinguishable by the difference of their conditions under the same causal laws. The differences between them only matter due to the assumption that different conditions lead to different results, which is deterministic causality. A possible world theorist would say that had I not got on a bus, at this time of writing this comment while I am on a bus, to say that it is true that it is possible for me to have written this comment while not on a bus is to say that a counterpart of myself in a different possible world would have had to have written it while not on a bus. Thus my claim “it is possible that I have written this comment while not on a bus” despite me being on a bus at time of writing it, would be ascertained as true if the potential to write it while I’m not on a bus is true on some potential world, physically detached from our own but truly existing. Possible world metaphysical theorists argue so to justify ascertaining whether claims about things being possible are true or false despite them not having occurred in our actual (meaning, the indexical mark of the one shared by the speaker and the reader) world.

[@bigol7169]

@@KaneB that is absolutely mind blowing. Wow. Thanks !!

[@bigol7169]

@@benzur3503 wow, are you a philosopher too? Very detailed response! And are you actually on a bus lol? .. Ok but surely this is about *initial* conditions, right? Because (on determinism) how could the current moment NOW lead to any result other than what results in our universe? Or is this like a branching theory of time, where the present moment has a bunch of possible futures, each of which can be thought of as a possible world? (Even if they don’t really exist). Sorry I don’t know much about this, I probably asked too much here. Any clarification is appreciated!

[@SmellySquid]

I will get back to this after I watch this, but reading the title I think you mean "possible but not actual worlds," as opposed to saying nothing is possible including this actuality.

[@KaneB]

I don't talk about this in this video, but I hold both (1) there are no modal properties, period, so nothing is possible or necessary (see the video linked in the pinned comment) and also (2) there is no actual world either. I intend to address (2) in a future video.

[@mileskeller5244]

One can not have facts about other possible worlds. It may be in the other world that physics and science does not work like it does here.

[@absupinhere]

There are no possible worlds. Including this one. Deus vult.

[@OBGynKenobi]

Isn't this just a fancy way to talk about probabilities?

[@benzur3503]

Nah. Possible worlds are used to ascertain causal claims, not comparative statistical odds. Where I say “in a possible world which shares our laws of physics where I caught that plate you tossed at me, I didn’t let it break” I’m not saying anything about how many times out of an infinity plate tosses I would have caught, I am pointing at the results and correlations of the action, not at its % out of the totality of existing potential events which share such qualities to the best of my estimation.

[@KaneB]

I suppose you could say that, in the sense that "possible worlds" is a fancy way of talking about modality in general, and probabilities are a particular type of modality. There are interpretations of probability that don't involve any commitment to possible worlds though; indeed we need not take probability to be an objective feature of the world at all (we can interpret it in terms of degrees of belief, say).

[@DigitalGnosis]

@@KaneB *way of talking* - you *said* it right there

[@benzur3503]

@@KaneB what’re some of these alternatives to ascertain truth or falsehood of a claim being possible?

[@deadman746]

Modal logic was just bullshit to defend the idea that Descartes fully understood how the human brain worked in 1638. None of this stuff works. At least Wittgenstein got better, though I always got the impression he was being more than a bit sarcastic with the _T L-P._

[@InventiveHarvest]

If you had worn a blue shirt, you could not have used wearing a blue shirt as a counter factual.

[@KaneB]

Actually I could have done, because there are also no colours, no shirts, and no people to wear them.

[@InventiveHarvest]

@@KaneB 'actually'

[@BumbleTheBard]

If you accept that modal logic and linguistics make successful use of possible worlds, then it seems to be problematic that they should be dismissed from metaphysics. People sometimes talk of "useful fictions" but that doesn't sit well with me. If they work, why are they false? In the last 50 years we have learned to link logic to metaphysics (I'm thinking particularly of Quine, Dummett and Williamson) so why shouldn't the success of modal logic count as evidence for the metaphysics? Skeptics owe us an explanation.

[@ericb9804]

possible worlds = one of the sillier ways philosophers over complicate the wholly obvious. As per usual, its our insistence on metaphysics that leads to our confusion.

[@hss12661]

But possible worlds were invented by Leibniz. And then advanced by i.e. Wittgenstein in the Tractatus before Kripke and Lewis did whatever they did. I don't think either Leibniz or Wittgenstein were right but possible worlds are an obvious consequence of logical atomism... and I don't think logical atomism is right either but it was certainly accepted among non-metaphysicians.

[@ericb9804]

@@hss12661 "Possible Worlds" is ontology and ontology is metaphysics. "Logical atomism" is also ontology and therefore also metaphsycis. From Stanford... Bertrand Russell (1872-1970) described his philosophy as a kind of “logical atomism”, by which he meant to endorse both a metaphysical view and a certain methodology for doing philosophy. The metaphysical view amounts to the claim that the world consists of a plurality of independently existing things exhibiting qualities and standing in relations.

[@hss12661]

@@ericb9804 If so, then everything is metaphysics.

[@kimyunmi452]

There are no contingenties either.

[@ostihpem]

Why must 1+1=2 be necessary, i.e. be true in every possible world. Why cant there be one possible world where contradictions are true, therefore 1+1=2 false?

[@amydurham5606]

This was brought up later when they talk about some things that are true in every possible [variation of our] world, but might not be true in some conceivable other world that has different fundamental rules. Kind of like how in every possible world from this point onward, i have eaten my sandwich - that will forever be true of any world that diverges from this one at any point after i've eaten said sandwich

[@Alex.G.Harper]

*the epistemological objection:* I believe in possible worlds. my access to having knowledge of possible worlds is in two parts: (1) is knowledge that there are other possible worlds and (2) is the knowledge that of the whole or part of some possible world. (2) is easy to explain access. in fact, i’ll leave parfit to explain: These various beliefs are about what must be true, in the strong sense that applies to every possible world. One example is the belief that 2 + 2 = 4. I shall call these our modal beliefs. As I have said, we are often claimed to have empirical evidence for the truth of some mathematical beliefs, which is given by the ways in which scientists use these beliefs to make many confirmable predictions. But these facts provide no evidence for the modal status of mathematical truths. Such facts could show only that these mathematical beliefs are always in fact true, given the actual laws lof nature, leaving it open whether these beliefs must be true. The skeptical argument that we are now discussing could be applied to these modal beliefs. Modal skeptics might first claim that these beliefs were advantageous. I have claimed that, when we have believed that (N) some belief must be true, it would have seldom helped us to believe that (O) we had a decisive reason to have this belief. But though we didn't need to have normative beliefs like (O), we may have been helped by having modal beliefs like (N). When we believe that some belief must be true, this may usefully strengthen this belief. And such modal beliefs may have helped us to form other true beliefs. Arithmetic provides one example. We might learn from experience that two plus two always in fact equals four, that two plus three always in fact equals five, and that two plus four always in fact equals six. But this way of forming such mathematical beliefs would be limited, and slow. To gain most of our mathematical knowledge, we may have needed to believe, even if only at an unconscious level, that mathematical beliefs are necessarily true, and that we could reach other such true beliefs by certain kinds of valid reasoning. Modal skeptics might also claim that (2) because these modal beliefs were advantageous, natural selection made us disposed to have them, and that (4) these beliefs would have been advantageous whether or not they were true. We might object that these beliefs could not have failed to be true, since two plus two would equal four in every possible world. But modal skeptics could defend (4) in a different way. When such modal beliefs were advantageous, by helping us to form true beliefs about the actual world, it was irrelevant whether these beliefs applied truly to other possible worlds. It would have been just as advantageous to believe that, in the actual world, given the actual laws of nature, two plus two always equals four. Nor does our logical reasoning need to involve such modal truths. Rather than using arguments that are modally valid, in the sense that, if their premises are true, their conclusions must be true, it would be enough if these arguments were factually valid, in the sense that, if their premises are true, their conclusions are always in fact true. If these modal beliefs were partly produced by natural selection, that would provide one challenge to these beliefs. Modal skeptics might claim that (4) natural selection would have disposed us to have these modal beliefs whether or not they were true. We must also admit that, as premise (6) claims, we have no empirical evidence for the truth of these beliefs. We cannot have any evidence about the many possible worlds in which the laws of physics, or other laws of nature, would have been different. As before, however, this argument needs another premise. Modal skeptics must claim that (7) we have no other way of knowing whether these beliefs are true. And we can reject this claim. Our cognitive abilities, we can assume, were partly produced by evolutionary forces. But these abilities later ceased to be governed by these forces, and had their own effects. Natural selection gave us wings, but when we could fly, we soared into the sky. We used these cognitive abilities to discover some new kinds of truths. Nagel gives, as one example, our understanding of arithmetical infinity. It would have been advantageous to form true arithmetical beliefs about various small numbers, such as how many lions have entered and left our cave. We discover infinity, Nagel writes: when we ask whether these numbers . .. are all there is. It is like stepping into what looks like a small windowless hut and finding oneself suddenly in the middle of a vast landscape stretching endlessly out to the horizon. Just as we could discover infinity, though this discovery was not advantageous, we could discover necessity. We could see that, if X implies Y, and X is true, Y must be true. This use of 'see' does not imply that we have some quasi-perceptual faculty. Such metaphors refer to the kind of rational insight that is involved in every step of valid reasoning. This ability is sometimes claimed to be mysterious. But when it seems to us clear that some belief must be true, there is nothing in our cognitive experience that is more transparent and intelligible, or less mysterious. The mystery could be only how we became to able to have these clear beliefs about these necessary truths. Even if we cannot yet explain how we came to have this ability, we can justifiably believe that we can recognize such necessary truths. For this skeptical argument to succeed, this argument must have premises which are more plausible than the modal beliefs which it claims to undermine. Two such beliefs are: (P) Two plus two must equal four, and (Q) No statement could be both wholly true and wholly false. This argument must assume that (R) we have no way of knowing whether such modal beliefs are true. Of these three claims, much the least plausible is (R). If (R) were true, we could not know whether (S) it might have been true that two plus two equals three, or five, or ninety nine. Nor could we know whether (T) it might have been true that our beliefs were both wholly true and wholly false. Since we can have no empirical evidence for modal truths, our modal beliefs raise deep and difficult questions. But we do know that two plus two must equal four, and that our beliefs could not be both wholly true and wholly false. We can know some things even if we don't yet know how we know them. Most earlier humans knew many truths about what they could see, hear, touch, and smell, though they didn't know how they knew these truths.

[@DaKoopaKing]

I hate how a lot of philosophers don't really seem to care to get at the fundamentals and will just appeal to common-sense principles without exploring their grounding. "(P) Two plus two must equal four," - we define numbers axiomatically to e.g. never loop on themselves and repeat. If we didn't, and we used a looping theory of numbers, we would say that 2+2 sometimes equals 4, sometimes not, depending on the axiom schema we're working with. If there's supposed to be this existing thing, a number, that somehow isn't what we define axiomatically, or that isn't a label we use to categorize physical phenomena, I'd love to hear what it is, because then we'd actually begin doing metaphysics. Absent this account, the statement (P) is irrelevant to Parfit's point. Might as well claim that because chess "must" be played with exactly 2 kings on the board otherwise it's not chess, we've discovered some deep necessary truth about chess - except of course we haven't, we've just reported people's (general) attitudes towards which pieces they prefer on the board during a chess game, which is itself constructed by people's concerning how they want to play the game.

[@KaneB]

I'm not seeing the relevance of all this. First, Parfit is responding there to an evolutionary debunking argument, but that's not an argument that I give in this video. Second, Parfit is responding to modal skeptics who deny that we are justified in believing modal claims. But again, that's not the position that I'm arguing for here. I'm assuming that there are modal truths, and that we know what at least some of the modal truths are. What I'm arguing for is that modal truths are not truths about possible worlds. Moreover, I don't think Parfit would disagree with this. At least in his later career, he favoured non-realist cognitivism about modal claims: as in the case of morality, some modal claims are true, but nothing makes them true: there is no part of reality that true modal claims correctly describe, or to which they correspond. Perhaps Parfit believes in possible worlds, but if so, he would take them to be irrelevant to the modal truths, just as I have argued here. Talk of "possible worlds" is just formal tool or a useful manner of speaking about modality. In any case, when Parfit actually addresses the epistemic access challenge there, it seems to me that all he's doing is table-thumping that we *do* know various modal truths and that this is more plausible than the skeptic's claim that there is no way of knowing them. Well, very well, perhaps that kind of Moorean argument is successful in justifying our modal beliefs. But it doesn't do anything to address the epistemic challenge. All it shows is that we are justified in continuing to hold modal beliefs even without a response to the epistemic access challenge. We can justifiably assume that there is some way of knowing the modal facts, even if we have no idea what this way is. This kind of response to epistemic access challenge might be plausible if we're just talking about modal facts. It is much less plausible when the epistemic access challenge is raised against possible worlds. Compare: (T1) Two plus two must equal four. (T2) There are possible worlds, and two plus two equals four in all worlds. (B1) There could have been blue swans. (B2) There are possible worlds, and in some world, there are blue swans. (T1) and (B1) are commonsensical, (T2) and (B2) are not. (T2) and (B2) are contentious theoretical claims, and I don't think they are at all more plausible than the skeptical challenge that we have no way to access facts about other worlds. Possible worlds, whether they are thought of as concrete entities or as abstractions of some kind, are not simply items of common sense that can be taken for granted for the purposes of forwarding a Moorean argument.

[@KaneB]

Also, my point with the epistemic access challenge is that thinking of modal truths as grounded in facts about possible worlds seems to create an access problem where intuitively there is none. For at least some modal truths, it seems very easy to account for how I know them - if you ask me how I know the proposition, "I could have worn a blue shirt", I could give a pretty good answer, by pointing out that I have a blue shirt in my closet, that I have worn blue shirts in the past, that there is no apparent obstacle between me and my closet, and so on. If you ask how I know that my counterpart in some other world is wearing a blue shirt, well, that question is a lot more puzzling.

[@patrickwrites]

Strange part is when modal realists claim the same kind of reasoning (for the actual existence of infinite worlds) applies elsewhere. There is no where it applies and no cultures that have anything remotely like that. It's such a bizarre move, but it does stand as a great counterexample to the "smart people believing something provides some evidence for that" claims.

[@TheoEvian]

When you say that "the fact another version of me won the election in a possible world doesn't make it possible for me to win it" you are forgetting that me and that other person share a different relationship than me and any other entity - a relationship of trans-world identity. He IS me, just in another world and if I could identify differences between us I could identify what made him actually win the election and me to actually lose it and I think that could be a useful insight. But anyway, I use possible worlds nomenclature to analyse fiction so I am not a modal realist, I believe that possible worlds are models and artefacts created by humans (when they read a book for example) and since in fiction you can easilly have impossible worlds too I use the term "fictional world" almost exclusively for what I am doing so I am not really invested in this debate.

[@KaneB]

Yeah, I don't really have any objection to possible worlds in that kind of fictionalist sense, where a "world" is basically just a story that we tell, and this doesn't have any implications for modal metaphysics. About the irrelevance point. I don't find most of the accounts of trans-world identity satisfying here. The only one I'm aware of that might work in my view would be a concretist modal realism with overlapping worlds - suppose that worlds literally branch as in the Everett interpretation of quantum mechanics, then "I could have worn a blue shirt" is true because, at the point where I decided which shirt to wear, the world branched and a version of me does choose a blue shirt. I say "might work" because even in this case, it strikes me as acceptable to deny that the version of Kane with the blue is me in the relevant sense. Moreover, that even if there had been no branching worlds, I would still assert things like, "I could have worn a blue shirt." Facts about other worlds just don't strike me as the right kind of thing to make modal propositions true.

[@TheoEvian]

@@KaneB Btw, this "splitting" (ramifying) nature as a characteristic of possible worlds is what some theoreticians (Marie-Laure Ryan? That other Finnish lady whose name I can't remember?) claim to be the main difference between possible worlds (that are supposed to have this feature where we can find the "point of departure" from the history of the actual world) and fictional worlds (which don't require any such thing). For me the trans-world identity becomes suspect when we say things like in the joke "would you love me if I were a worm?" Like what makes the special relationship between me and the worm even true? But on the other hand we have no problem thinking about such an extreme relationship in general, we do it since early childhood and quite naturally even with low inteligence which is illustrated by the presence of beings such as "snake Hitler" in Rick and Morty (sarcasm). Like there is a surprising number of books where Napoleon is not the Emperor of France and people still have no problem thinking "yeah, that guy in the book IS Napoleon". But that's too far afield for this discussion. Reading is fun.

[@TheoEvian]

@@KaneB Ok, I checked, it was actually Ruth Ronnen the one person with ramification.