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10. Modality / E. Possible worlds / 1. Possible Worlds / e. Against possible worlds

[there is no such thing as a 'possible world']

29 ideas
Possible worlds are a way to dramatise essentialism, and yet they presuppose essentialism [Quine]
     Full Idea: Talk of possible worlds is a graphic way of waging the essentialist philosophy, but it is only that; it is not an explication. Essence is needed to identify an object from one possible world to another.
     From: Willard Quine (Intensions Revisited [1977], p.118)
     A reaction: He makes the proposal sound circular, but I take a commitment to essences to be prior to talk of possible worlds. Possible worlds are a tool for clarifying modalities, not for clarifying essential identities.
Possible worlds don't fix necessities; intrinsic necessities imply the extension in worlds [Armstrong]
     Full Idea: It seems natural and plausible to say that it is the fact that a necessary truth is itself necessary that determines its truth in all possible worlds. This intension determines its extension across possible worlds.
     From: David M. Armstrong (Truth and Truthmakers [2004], 08.1)
     A reaction: Well said. To me (but not to Armstrong) this implies essentialism, that the necessity arises from the intrinsic natures of the things involved. The whole Lewisian approach of explaining things by mapping them strikes me as wrong.
Possible worlds are useful in set theory, but can be very misleading elsewhere [Kripke]
     Full Idea: The apparatus of possible worlds has (I hope) been very useful as far as the set-theoretic model-theory of quantified modal logic is concerned, but has encouraged philosophical pseudo-problems and misleading pictures.
     From: Saul A. Kripke (Naming and Necessity notes and addenda [1972], note 15)
     A reaction: This is presumably a swipe at David Lewis, who claims possible worlds are real. The fact that the originator of possible worlds sees them as unproblematic doesn't mean they are. Fine if they are a game, but if they assert truth, they need a metaphysics.
Mathematical sentences are a problem in a possible-worlds framework [Jackson]
     Full Idea: There is notoriously a problem about what to say concerning mathematical sentences within the possible-worlds framework.
     From: Frank Jackson (From Metaphysics to Ethics [1998], Ch.3 n25)
     A reaction: Presumably this concerns possible axioms and their combinations.
Possible worlds rely on what might have been, so they can' be used to define or analyse modality [Salmon,N]
     Full Idea: On my conception, the notions of metaphysical necessity and possibility are not defined or analyzed in terms of the apparatus of possible worlds. The order of analysis is just the reverse: possible worlds rely on the notion of what might have been.
     From: Nathan Salmon (The Logic of What Might Have Been [1989], IV)
     A reaction: This view seems to be becoming the new orthodoxy, and I certainly agree with it. I have no idea how you can begin to talk about possible worlds if you don't already have some idea of what 'possible' means.
If other worlds exist, then they are scattered parts of the actual world [Jubien]
     Full Idea: Any other realms that happened to exist would just be scattered parts of the actual world, not entire worlds at all. It would just happen that physical reality was fragmented in this remarkable but modally inconsequential way.
     From: Michael Jubien (Analyzing Modality [2007], 1)
     A reaction: This is aimed explicitly at Lewis's modal realism, and strikes me as correct. Jubien's key point here is that they are irrelevant to modality, just as foreign countries are irrelevant to the modality of this one.
If all possible worlds just happened to include stars, their existence would be necessary [Jubien]
     Full Idea: If all of the possible worlds happened to include stars, how plausible is it to think that if this is how things really are, then we've just been wrong to regard the existence of stars as contingent?
     From: Michael Jubien (Analyzing Modality [2007], 1)
If there are no other possible worlds, do we then exist necessarily? [Jubien]
     Full Idea: Suppose there happen to be no other concrete realms. Would we happily accept the consequence that we exist necessarily?
     From: Michael Jubien (Analyzing Modality [2007], 1)
Possible worlds just give parallel contingencies, with no explanation at all of necessity [Jubien]
     Full Idea: In the world theory, what passes for 'necessity' is just a bunch of parallel 'contingencies'. The theory provides no basis for understanding why these contingencies repeat unremittingly across the board (while others do not).
     From: Michael Jubien (Analyzing Modality [2007], 1)
Worlds don't explain necessity; we use necessity to decide on possible worlds [Jubien]
     Full Idea: The suspicion is that the necessity doesn't arise from how worlds are, but rather that the worlds are taken to be as they are in order to capture the intuitive necessity.
     From: Michael Jubien (Analyzing Modality [2007], 1)
     A reaction: It has always seemed to me rather glaring that you need a prior notion of 'possible' before you can start to talk about 'possible worlds', but I have always been too timid to disagree with the combination of Saul Kripke and David Lewis. Thank you, Jubien!
We have no idea how many 'possible worlds' there might be [Jubien]
     Full Idea: As soon as we start talking about 'possible world', we beg the question of their relevance to our prior notion of possibility. For all we know, there are just two such realms, or twenty-seven, or uncountably many, or even set-many.
     From: Michael Jubien (Analyzing Modality [2007], 1)
The love of possible worlds is part of the dream that technical logic solves philosophical problems [Jubien]
     Full Idea: I believe the contemporary infatuation with possible worlds in philosophy stems in part from a tendency to think that technical logic offers silver-bullet solutions to philosophical problems.
     From: Michael Jubien (Possibility [2009], 3.2)
     A reaction: I would say that the main reason for the infatuation is just novelty. As a technical device it was only invented in the 1960s, so we are in a honeymoon period, as we would be with any new gadget. I can't imagine possible worlds figuring much in 100 years.
Possible worlds don't explain necessity, because they are a bunch of parallel contingencies [Jubien]
     Full Idea: The fundamental problem is that in world theory, what passes for necessity is in effect just a bunch of parallel 'contingencies'.
     From: Michael Jubien (Possibility [2009], 3.2)
     A reaction: Jubien's general complaint is that there is no connection between the possible worlds and the actual world, so they are irrelevant, but this is a nicely different point - that lots of contingent worlds can't add up to necessity. Nice.
Lewis must specify that all possibilities are in his worlds, making the whole thing circular [Shalkowski, by Sider]
     Full Idea: If purple cows are simply absent from Lewis's multiverse, then certain correct propositions turn out to be impossible. Lewis must require a world for every possibility. But then it is circular, as the multiverse needs modal notions to characterize it.
     From: report of Scott Shalkowski (Ontological Ground of Alethic Modality [1994], 3.9) by Theodore Sider - Reductive Theories of Modality 3.9
     A reaction: [Inversely, a world containing a round square would make that possible] This sounds very nice, though Sider rejects it (p.197). I've never seen how you could define possibility using the concept of 'possible' worlds.
If possible worlds are just fictions, they can't be truthmakers for modal judgements [Heil]
     Full Idea: If the other possible worlds are merely useful fictions, we are left wondering what the truthmakers for all those modal judgements might be.
     From: John Heil (The Universe as We Find It [2012], 08.07)
     A reaction: I suddenly see that this is the train of thought that led me to believe in real powers and dispositions, and which retrospectively led me to love the truthmaker idea. Even real Lewisian worlds don't seem adequate as truthmakers here.
Does every abstract possible world exist in every possible world? [Lowe]
     Full Idea: Possible worlds, conceived of as abstracta, surely exist 'in every possible world'.
     From: E.J. Lowe (The Possibility of Metaphysics [1998], 12)
     A reaction: A possible very infinite regress, if a particular possible world is distinguished from another only by being perceived from Actual Word 1 or Actual World 2.. How many possible worlds are there? The standard answer is 'lots', rather than infinity.
We could give up possible worlds if we based necessity on essences [Lowe]
     Full Idea: If we explicate the notion of metaphysical necessity in terms of the notion of essence, rather than vice versa, this may enable us to dispense with the language of possible worlds as a means of explicating modal statements.
     From: E.J. Lowe (What is the Source of Knowledge of Modal Truths? [2013], 6)
     A reaction: This is the approach I favour, though I am not convinced that the two approaches are in competition, since essentialism gives the driving force for necessity, whereas possible worlds map the logic and semantics of it.
One might hope to reduce possible worlds to properties [Swoyer]
     Full Idea: One might hope to reduce possible worlds to properties.
     From: Chris Swoyer (Properties [2000], 4.1)
     A reaction: [He cites Zalta 1983 4.2, and Forrest 1986] I think we are dealing with nothing more than imagined possibilities, which are inferred from our understanding of the underlying 'powers' of the actual world (expressed as 'properties').
Realism about possible worlds is circular, since it needs a criterion of 'possible' [Oderberg]
     Full Idea: Any realist theory of possible worlds will be circular in its attempt to illuminate modality, for there has to be some criterion of what counts as a possible world.
     From: David S. Oderberg (Real Essentialism [2007], 1.1)
     A reaction: Seems right. At the very least, if we are going to rule out contradictory worlds as impossible (and is there a more obvious criterion?), we already need to understand 'impossible' in order to state that rule.
Possible worlds make every proposition true or false, which endorses classical logic [Hale]
     Full Idea: The standard conception of worlds incorporates the assumption of bivalence - every proposition is either true or false. But it is infelicitous to build into one's basic semantic machinery a principle endorsing classical logic against its rivals.
     From: Bob Hale (Necessary Beings [2013], 10.3)
     A reaction: No wonder Dummett (with his intuitionist logic) immediately spurned possible worlds. This objection must be central to many recent thinkers who have begun to doubt possible worlds. I heard Kit Fine say 'always kick possible worlds where you can'.
If some book described a possibe life for you, that isn't what makes such a life possible [Jacobs]
     Full Idea: Suppose somewhere deep in the rain forest is a book that includes a story about you as a truck-driver. I doubt that you would be inclined the think that that story, that book, is the reason you could have been a truck driver.
     From: Jonathan D. Jacobs (A Powers Theory of Modality [2010], §3)
     A reaction: This begins to look like a totally overwhelming and obvious reason why possible worlds (especially as stories) don't give a good metaphysical account of possibility. They provide a semantic structure for modal reasoning, but that is entirely different.
Possible worlds semantics gives little insight into modality [Jacobs]
     Full Idea: If we want our semantics for modality to give us insight into the truthmakers for modality, then possible worlds semantics is inadequate.
     From: Jonathan D. Jacobs (A Powers Theory of Modality [2010], §4.4)
     A reaction: [See the other ideas of Jacobs (and Jubien) for this] It is an interesting question whether a semantics for a logic is meant to give us insight into how things really are, or whether it just builds nice models. Satisfaction, or truth?
Possible worlds models contain sets of possible worlds; this is a large metaphysical commitment [Horsten/Pettigrew]
     Full Idea: Each possible worlds model contains a set of possible worlds. For this reason, possible worlds semantics is often charged with smuggling in heavy metaphysical commitments.
     From: Horsten,L/Pettigrew,R (Mathematical Methods in Philosophy [2014], 3)
     A reaction: To a beginner it looks very odd that you should try to explain possibility by constructing a model of it in terms of 'possible' worlds.
Using possible worlds for knowledge and morality may be a step too far [Horsten/Pettigrew]
     Full Idea: When the possible worlds semantics were further extended to model notions of knowledge and of moral obligation, the application was beginning to look distinctly forced and artificial.
     From: Horsten,L/Pettigrew,R (Mathematical Methods in Philosophy [2014], 5)
     A reaction: They accept lots of successes in modelling necessity and time.
Possibilities are like possible worlds, but not fully determinate or complete [Rumfitt]
     Full Idea: Possibilities are things of the same general character as possible worlds, on one popular conception of the latter. They differ from worlds, though, in that they are not required to be fully determinate or complete.
     From: Ian Rumfitt (The Boundary Stones of Thought [2015], 6)
     A reaction: A rather promising approach to such things, even though a possibility is fairly determinate at its core, but very vague at the edges. It is possible that the UK parliament might be located in Birmingham, for example. Is this world 'complete'?
If a world is a fully determinate way things could have been, can anyone consider such a thing? [Rumfitt]
     Full Idea: A world is usually taken to be a fully determinate way that things could have been; but then one might seriously wonder whether anyone is capable of 'considering' such a thing at all.
     From: Ian Rumfitt (Logical Necessity [2010], §4)
     A reaction: This has always worried me. If I say 'maybe my coat is in the car', I would hate to think that I had to be contemplating some entire possible world (including all the implications of my coat not being on the hat stand).
Every philosophical theory must be true in some possible world, so the ontology is hopeless [Ingthorsson]
     Full Idea: Possible worlds ontology appears to be plentiful enough to allow every philosophical theory to be true in some world or other, and that is why I cannot consider it an ontologically serious theory. It admits everything and forbids nothing
     From: R.D. Ingthorsson (A Powerful Particulars View of Causation [2021], 9.6)
     A reaction: Nice. Be careful what you wish for. The theory would have to be consistent (unless we also accept impossible worlds).
Worlds may differ in various respects, but no overall similarity of worlds is implied [Ingthorsson]
     Full Idea: Even if possible worlds could differ in many different respects, there is no useful way to combine these different respects into one measure of overall comparative similarity.
     From: R.D. Ingthorsson (A Powerful Particulars View of Causation [2021], 9.7)
     A reaction: [idea of Michael Moreau 2010] This is an objection to the use of 'close' possible worlds in causation theories. The idea is true in general of the concept of similarity. It makes sense of specific 'respects', but not really of two whole objects.
Dispositionalism says modality is in the powers of this world, not outsourced to possible worlds [Friend/Kimpton-Nye]
     Full Idea: Dispositionalism does not 'outsource' modality to other possible worlds, it roots modality in the powers of concrete individuals in this world.
     From: Friend/Kimpton-Nye (Dispositions and Powers [2023], 3.3.3)
     A reaction: Possible worlds are to abolish modality, by treating it as the non-modal facts of different worlds. I see the dispositional view as vastly superior, because the world is awash with vivid and undeniable potentialities, and one world is better ontology.