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- เผยแพร่เมื่อ 23 ก.ค. 2024
- I examine five objections to modal realism: (1) Modal realism commits us to an unacceptable ontology; (2) What happens at other possible worlds is simply irrelevant to the modal facts at this world; (3) Modal realism undermines modal knowledge; (4) Many possibilities are excluded by modal realism, hence it is an inadequate account of modality; (5) Modal realism leads to moral indifference.
thank you!
modal realism ( sort of transcending fiction or hyper abstract?) reminds me of kant's noumenal world(things as really are?).
7:00 ontological /theoretical parsimony
9:00 irrelevant
16:00 causal condition &9th planet
18:00 mathematical identities
19:30 contigent & necessary facts
23:30 modal fact
26:00 modal realism capture all the possibilities /maximal spatio-temporal
28:00 island universe
31:00 world of nothing
31:48 moral paralysis
Very clear, systematic philosophy. Well done.
Currently revising for Philosophy finals, and this is a lifesaver! Brilliant
1-how similarity should exist between x and y,to be able to say that x is a counterpart of y?
2-when i say john searle could have been an economist,what i mean;
Suppose john searle is in a sequential game (searle's game ) in which he can choose t1 or t2 ,and if he chooses t1 then he can choose either s1 or s2, but if he chooses t2 then he either chooses r1 or r2.
Now suppose searle chooses t1 and then s1 and suppose that this path (t1,s1) is the path to a philosopher,and suppose that the path (t2,r2) is the path to be an economist.
Now when i say john searle could have been an economist,i mean john searle could have chosen (t2,r2), that's i'm talking about the first john searle who had chosen to be a philosopher and at the world in which he had chosen to be a philosopher,and not about his counterpart who exists in a different world.
So
P1-searle's game.
P2- modal realism doesn't explain the possibility in searle's game.
P3- if searle's game and modal realism doesn't explain the possibility in searle's game,then there's something important to modal realism which it doesn't explain.
Could Lewis hold that the supposed "island universes" we're thinking of aren't actually two disconnected spacetimes that are both somehow 'within' or 'part of' one world, but are actually just two distinct worlds? What would it even be for a world to contain multiple disconnected spacetimes?
Modal Realism and Don Van Vliet in the same video. You just got a new subscriber lmao
3:00 "All things that can exist do exist" seems simpler, to me, than "some things that can exist do exist but some things that can exist do not exist," as you would seemingly need some special reason for some possibilities being actual, which the modal realist doesn't need. People ask "why is there something rather than nothing" but not "why is there this particular something rather than all the equally possible somethings," which seems just as big an issue, and one that modal realism seemingly lets us avoid.
33:00 surely that problem applies if the spatial universe is infinitely large (as it seems to be). If so you couldn't change the amount of good and evil in total
Hello! In this year I´m going to do my thesis for my bachelor's degree. I´m really interested to do it in Logic. I find modal logic very interesting, and your videos about Quine and Modal realism really usefull. I´m thinking to do something about the last topic, can you recomend me some books? I only dowloaded the book of possible worlds of Lewis.
Really sorry for my bad english, I´m spanish speaker, and also thinking to fo to UK to do my master and PhD in logic :D
I have just completed my thesis for my bachelor's degree and it was about modal logic (more specifically: deontic logic). I found that some good books were:
Fitting, M. and Mendelsohn, R. L. [2012], First-order modal logic
Gamut, L. [1991], Logic, Language, and Meaning: Intensional logic and logical
grammar, Vol. 2
Hughes, G. E. and Cresswell, M. J. [1996], A new introduction to modal logic
These might help you out, they aren't specifically about modal realism though.
Hi, I enjoy your videos a lot and hope you see this. Around the 30th minute of this video you say there's a possible inconsistency in Lewis's theory, because he says 1. It's impossible for there to be completely disconnected spacetimes and 2. That there are many worlds which are spatiotemporally disconnected. But isn't a precise reading of 1. actually "it's impossible for *one* world to have multiple spatiotemporally disconnected parts"? If you read 1. this way, the inconsistency disappears.
Okay. But it’s not obviously impossible. In fact, if anything, it’s obviously coherent. Lewis is cooked on this point.
18:15 I'm so confused. I'm like 99% sure that David Lewis has always been a very committed Nominalist, so I'm not sure where you got that from
It's a summary of Lewis's own argument in The Plurality of Worlds, 2.4 "How can we know?". Lewis's point is that we are not causally acquainted with mathematical objects, and nevertheless it is obvious that we have knowledge of them. In that passage he doesn't say that they are abstract objects, but he does accept that mathematics is a "causally inaccessible realm of special objects" (at least until we can provide an "ontologically innocent" interpretation of that realm).
The island universe objection is a knockdown objection to Lewis’ version of modal realism. It’s clearly logically possible for there to be two disconnected spacetimes. And for Lewis to call that a mere intuition is a strawman and ignores the objection.
Could Lewis hold that the supposed "island universes" we're thinking of aren't actually two disconnected spacetimes that are both somehow 'within' or 'part of' one world, but are actually just two distinct worlds? What would it even be for a world to contain multiple disconnected spacetimes?
I am no philosopher so I can't follow but I find the concept of modal realism very attractive because one theory replaces here all the theories needed to explain the exact value of all these forces, weights of particles... I am still puzzled if all the universes that differ only a tiny bit can't be "grouped" into "sets" somehow, like any point would be surrounded by a cloud of other possible states but still forming the same universe until the whole thing differs so much that only then a new universe is required to make it stable. Of course it would be nice if the cloud of virtual particles surrounding any particle is exactly what I describe, but it seems not I heard from someone more knowledgeable.
It's not clear that modal facts are not contingent in modal realism. Hitler winning the war would be a contingent fact no matter which world it happens in, and under modal realism in order for it to be possible a counterpart of Hitler must have actually done it in some world. No amount of recombination can let us peer into another world and check that this contingent thing happened there.
The principle of recombination seems to be just exactly linguistic ersatzism. Somehow Lewis is inferring that if something is possible in linguistic ersatzism then there must be a real world where it happens, but it's not clear how.
25:18 "Linguistic ersatzism says that possible worlds are maximal consistent sets of propositions, but we don't see maximal consistent sets of propositions just hanging in the air."
Linguistic ersatzism specifies exactly how we can investigate possible worlds. Possible worlds are sets of propositions, not places we might have to visit in order to learn about them. Under modal realism one can easily argue that we must visit a possible world in order to truly determine that it is possible. This is a direct consequence of how modal realism defines possibility, even if it does contradict how Lewis tells us to investigate possibility by recombination.
Under linguistic ersatzism we have a different idea of what makes something possible, and this one is far more convenient to use in practice. You can think about a set from an armchair and if it follows the rules of linguistic ersatzism then by fiat it is a possible world independent of any other consideration.
+Ansatz66
"It's not clear that modal facts are not contingent in modal realism. Hitler winning the war would be a contingent fact no matter which world it happens in, and under modal realism in order for it to be possible a counterpart of Hitler must have actually done it in some world."
To say that a fact is contingent is to say that it could have failed to obtain. On modal realism, modal facts couldn't have failed to obtain. E.g. it couldn't have failed to be the case that in some possible worlds, Hitler's counterparts lose WWII. "It could have failed to be the case that X" means that X doesn't occur in some possible worlds. But "in some possible worlds, Hitler's counterparts win WWII" is true in every world.
You're right that we can't peer into other worlds to check what the modal facts are. But the modal facts, whatever they are, are necessary facts on modal realism. *If* it's true that at some worlds, Hitler's counterparts win WWII, then "at some worlds, Hitler's counterparts win WWII" is true at every world, hence necessarily true.
"Under linguistic ersatzism we have a different idea of what makes something possible, and this one is far more convenient to use in practice. You can think about a set from an armchair and if it follows the rules of linguistic ersatzism then by fiat it is a possible world independent of any other consideration.?"
What are the maximal consistent sets of propositions? If they're just parts of our minds, there's no problem investigating worlds. The obvious difficulty with this account is nobody has ever entertained or could ever entertain in their mind a maximal consistent set of propositions (let alone all the maximal consistent sets of propositions corresponding to all the possible worlds). So linguistic ersatzists will usually assume a platonist conception of propositions - propositions exist as mind-independent abstract object somehow. This is a popular way of viewing propositions in philosophy. See e.g.: plato.stanford.edu/entries/propositions/#nature
But on this view, it seems to me that linguistic ersatzism has exactly the same problem that modal realism does. We can't interact with abstract objects, so we can't interact with propositions.
Kane B "But the modal facts, whatever they are, are necessary facts on modal realism."
This could get confusing because modal realism is in the business of defining modality, so there are at least two senses in which a fact can be necessary. For one, a fact can be necessary because modal realism defines it to be necessary, meaning that it is true in every world.
A fact could also be necessary in the sense that nothing can depend counterfactually on it, and this sense is not obviously the same as the first one.
For example, suppose Hitler's counterpart lost the war in every world where Hitler has a counterpart. In this case, by the definition of modal realism, it was necessary for Hitler to lose the war. At the same time, it makes sense to say that if Hitler won the war then the Nazi party would rule Europe. Since that is a counterfactual, that fact would be necessary by modal realism but contingent by counterfactual.
Would modal realists accept that we could have meaningful counterfactuals about necessary facts, or would they attempt to somehow show that the worlds contain no such facts?
"What are the maximal consistent sets of propositions?"
Surely for a linguistic ersatzist a maximal consistent set of propositions is going to be a linguistic structure, a string of words with meanings. A platonist might tie that to some abstract thing that exists in some sense, but whether that is true or not is irrelevant to linguistic ersatzism since we don't need to know about that in order to determine that the set is consistent by the rules of the language. All we need are the words and the rules.
"The obvious difficulty with this account is nobody has ever entertained or could ever entertain in their mind a maximal consistent set of propositions."
If you mean that we cannot have a list of all the propositions then that is certainly true, especially since the list would be infinite. Even so, that is not actually a difficulty since the human mind is capable of thinking using abstractions.
For example, suppose that we want to say that a certain glass could break. To construct a linguistic possible world for that possibility, we can start by including all the true propositions of the actual world. Linguistic ersatzism fundamentally assumes that there are no contradictions in the actual world, so there's no need to check for that. Next we remove all propositions that entail the glass is unbroken. If there is some unknown law of physics protecting the glass, we can consider the law repealed without ever considering the law specifically. Since removing propositions can't cause new propositions to be entailed, there's no need to check for contradictions here either.
Next we have to introduce the propositions entailed by the glass being broken. Since we previously removed all conflicting propositions from the list, we know that no contradiction can occur that way. The only thing we have to check is for contradictions within the broken glass itself. In other words, it is possible for the glass to be broken if and only if there is no contradiction within the concept of the glass being broken, with no need to consider the rest of the world's propositions.
There is still an infinite number of propositions needed to represent the broken glass, but once again abstraction saves us from having to think about them all. We know that all of those propositions take the form of a bit of glass being moved to some place in the world, so we can consider them all at once without listing them. These propositions could contradict if two bits of glass were supposed to be in the same place, at the same time, but we know there are plenty of places to accommodate every bit of glass without conflict. Therefore without needing to think about where each bit of glass would go we can confirm that there is no contradiction in the glass being broken.
"So linguistic ersatzists will usually assume a platonist conception of propositions - propositions exist as mind-independent abstract object somehow."
Why would they do that when it is in no way helpful?
+Ansatz66 "At the same time, it makes sense to say that if Hitler won the war then the Nazi party would rule Europe."
On modal realism that wouldn't make much sense - it would be like saying "if 2+2 hadn't been equal to 5, then ..." The reason why it's sensible to assert counterfactuals with antecedents "if Hitler had won the war" is precisely that Hitler's winning the war is possible. If that wasn't possible, it wouldn't be sensible to assert such counterfactuals. At least, that's Lewis's argument.
Re linguistic ersatzism, the maximal consistent sets of propositions can't literally be "a linguistic structure, a string of words with meanings". There is no such structure. There are no sets of sentences with the appropriate meanings. Rather, propositions are the meanings themselves, and meanings aren't the same as the words that express those meanings (again, recall the "snow is white" and "Schnee ist weiss" example).
"To construct a linguistic possible world for that possibility, we can start by including all the true propositions of the actual world"
If propositions are just parts of our minds, then the set of propositions true of the actual world is woefully incomplete. I'm not sure how the fact that we can "think using abstractions" is supposed to help here. To say that we're dealing with an abstraction of our set of maximal consistent of propositions is just to say that we don't have a maximal consistent set of propositions (the set of propositions will fail to be maximal). On the other hand, if propositions aren't parts of our minds, then it looks like we're moving towards a platonistic conception of them, in which case the skeptical problem arises.
"Why would they do that when it is in no way helpful?"
Because (1) in general, that's a popular way of conceiving of propositions, as noted in the link I gave and (2) as I noted, it avoids the problem that nobody has ever entertained a maximal consistent set of propositions.
Kane B "The reason why it's sensible to assert counterfactuals with antecedents 'if Hitler had won the war' is precisely that Hitler's winning the war is possible."
Any string of words takes its meaning from the rules of the language, and in English "If Hitler had won the war" has a very clear meaning. Under linguistic ersatzism a counterfactual can only have meaning if it is a possibility because of how linguistic ersatzism defines possibility.
In contrast, modal realism defines possibility according to the real worlds out there, and that means we need to face the epistemic possibility that those worlds do not include worlds that correspond to the set of all meaningful English counterfactuals. Modal realism cannot guarantee that because it does not define that to be true in the way that linguistic ersatzism does.
"The maximal consistent sets of propositions can't literally be 'a linguistic structure, a string of words with meanings'."
That seems fair. I should have said, a maximal consistent set of propositions is _the meaning_ of the linguistic structure rather than the linguistic structure itself. It is a subtle point, but you are perfectly correct.
"If propositions are just parts of our minds, then the set of propositions true of the actual world is woefully incomplete. I'm not sure how the fact that we can 'think using abstractions' is supposed to help here."
While there is great confusion over what a platonist means by an abstraction, there should be no need for such confusion over the meaning of abstraction within a person's mind. An abstraction just means thinking about things with certain details deliberately omitted from our thoughts. Let's not ignore the power of abstractions because it allows us to think about things that would be too complicated to think about otherwise.
For example, you can usefully think of The Mona Lisa as an abstraction and reach many true conclusions even while many details are omitted. For example, I don't need to think about the exact position and color of every speck of paint to determine that she has no eyebrows. I don't need to be aware that The Mona Lisa is painted on wood to determine that she has her hands crossed. There are many ways we can analyze The Mona Lisa even while being totally unaware of an uncountable number of details.
For another example, you may consider the set of all integers. You cannot do this by considering each individual integer, and yet the set as a whole still has meaning in your mind and you are capable of reasoning about it. You're aware that the set is infinite even though you've never given a moment's thought to even a tenth of the members of the set. This is because you can think using abstractions.
In the same way, we can think about the set of true propositions in the actual world as an abstraction without needing to think about each individual member of the set. In this way the set of propositions can exist in your mind even though listing them all would be impossible.
"To say that we're dealing with an abstraction of our set of maximal consistent of propositions is just to say that we don't have a maximal consistent set of propositions."
I'm not sure I know what you mean by that, but I guess you're saying that we don't have the set unless we can enumerate the members of the set. The power of abstractions is that it allows us to think usefully about things without needing to consider every detail. The very reason we talk about sets is so that we don't always need to enumerate each item. I think we can rest assured that a linguistic ersatzist is not expecting a list of every member when she talks about maximal sets of propositions; she's talking about abstract sets.
"(1) In general, that's a popular way of conceiving of propositions."
An appeal to popularity shouldn't be worth even considering.
"(2) It avoids the problem that nobody has ever entertained a maximal consistent set of propositions."
That's not a real problem. It seems that the idea of that problem comes from a misunderstanding of how people think about sets, such as thinking that in order to consider a set one needs to consider all of its members.
+Ansatz66 "While there is great confusion over what a platonist means by an abstraction, there should be no need for such confusion over the meaning of abstraction within a person's mind."
I'm not confused about that. I'm saying I don't see how appealing to abstractions in people's minds is supposed to help the linguistic ersatzist here. An abstraction of a maximal consistent set of propositions isn't a maximal consistent set of propositions. An abstraction of such a set omits some of the propositions of that set. So it's not maximal. So it's not what the linguistic ersatzist needs.
"In this way the set of propositions can exist in your mind even though listing them all would be impossible."
No, they don't exist in your mind. *The abstraction of that set of propositions* exists in your mind. Similarly, when you abstract from the set of all integers, it's not that all the integers exist in your mind. Only the abstraction of the set of integers exists in your mind. An abstraction of X and X itself are not the same thing.
"I'm not sure I know what you mean by that, but I guess you're saying that we don't have the set unless we can enumerate the members of the set"
Correct - unless, of course, we take the set to exist independent of our minds, which is how most linguistic ersatzists treat their maximal consistent sets of propositions (and how mathematical platonists treat the integers).
"The power of abstractions is that it allows us to think usefully about things without needing to consider every detail"
Sure. But how does that help the linguistic ersatzist show that there are literally maximal consistent sets of propositions? Again, an abstraction of X isn't X.
"An appeal to popularity shouldn't be worth even considering"
It's not an appeal to popularity. You asked me why many linguistic ersatzists accept a platonist conception of propositions. Well, many philosophers in general accept a platonist account of propositions. So it's to be expected that many linguistic ersatzists will. For many philosophers, platonism about propositions is attractive in general, independent of linguistic ersatzism. (As for the arguments in favour of a platonist account of propositions independent of linguistic ersatzism, the SEP link I gave you might be a good place to start.)
"That's not a real problem"
It's generally considered to be a problem, and a platonist account of propositions solves it. Again, I'm just answering your question about why many linguistic ersatzists accept a platonist account of propositions.