Fifth Anniversary of Beginning Sprachlogik

February 24 this year marks the fifth anniversary of the first Sprachlogik post.

Thanks to everyone who has been supportive of the blog!

Sider's Quasi-Conventionalism About Modality

Starting in his (2003), and in an unpublished draft from around the same time which is not to be cited, Theodore Sider has proposed a theory of necessity de dicto called quasi-conventionalism. The most up to date version can be found in his (2011) and his replies to a symposium on that work. It states necessary and sufficient conditions for a proposition to be necessary, but as we will see, one of the key concepts involved has been left open-ended, so the account is to be regarded as partial. The account is supposed to reduce necessity de dicto to non-modal notions, and to be extendable to de re modality.

What makes Sider’s account so worthy of discussion from my point of view is that it takes what I believe to be an important step forward with respect to the task of giving an account of necessity de dicto. The step forward is that it embodies a certain structure, which my account shares. Abstracting from the details of Sider’s account, the shared structure can be expressed in the form of a schematic analysis as follows:

(Schema) A proposition is necessary iff it is, or is implied by, a proposition which is both true and meets a certain condition C.

(Sider, as we shall see, does not quite use his schema, but his analysis can easily be re-expressed so as to conform to it.)

So, Sider’s view takes, as I will argue, an important step forward. But it also has grave defects. Considering Sider’s view, then - seeing that it instantiates the suggestive and appealing (Schema), and seeing what is wrong with it - offers a nice way of leading up to and motivating my own account, which I will give in the next chapter. (This is not the way I actually arrived at my account, but it could have been.)

Two of SIder’s main starting points seem to be: (i) the desire to find a way of reducing modal concepts to non-modal concepts, and (ii) a hunch that conventionalist theories according to which necessities are true by convention were on to something: roughly, that convention should play some key role in the analysis of necessity. Regarding (i) and the underlying motivation for it, there are two interrelated strands here: one is a relatively theory-neutral feeling that modality is mysterious, or cries out for explanation, but this then plays into the second strand, which is emphasized in his (2011): a desire for an account of the “fundamental nature of reality”, “reality’s fundamental structure” - an account that “carves nature at the joints”.

Sider argues that it was always a mistake to try to account for necessary truth by means of the idea of truth by convention: the idea is of dubious coherence, and in view of necessary a posteriori truths especially, would not seem to line up with the idea of necessary truth anyway. But that doesn’t mean convention can’t play a crucial role in, not truth-making, but necessity-making, or accounting for the necessity of necessary truths. (I make the analogous point, with the meanings or natures of propositions in place of convention, in arguing for my account.) Part of the motivation and attraction of truth by convention theories of necessity, Sider allows, was their promise of shedding light on the epistemology of logic and mathematics. The theory of modality Sider is offering makes no claim to do that. But so what? Who says the place to look for insight into the epistemology of logic and mathematics is in a theory of modality?

In his (2011), Sider labels his account ‘Humean’. Here is his first pass at expressing it there:

To say that a proposition is necessary, according to the Humean, is to say that the proposition is i) true; and ii) of a certain sort. A crude Humean view, for example, would say that a proposition is necessary iff it is either a logical or mathematical truth. What determines the “certain sort” of propositions? Nothing “metaphysically deep”. For the Humean, necessity does not carve at the joints. There are many candidate meanings for ‘necessary’, corresponding to different “certain sorts” our linguistic community might choose. (Sider 2011, p. 269.)

The role of convention in Sider’s account, then, lies in distinguishing this “certain sort” - or “certain sorts” (Sider switches as this point to the plural):

Perhaps the choice of the “certain sorts” is conventional. Convention can do this without purporting to make true the statements of logic or mathematics (or, for that matter, statements to the effect that these truths are necessary), for the choice of the certain sorts is just a choice about what to mean by ‘necessary’. Or perhaps the choice is partly subjective/projective rather than purely conventional. (p. 270.)

As can be seen at the end of this last quote, Sider has some uncertainty about whether the choice of the “certain sorts” is ‘purely conventional’. We will not get deeply into Sider’s ideas of ‘conventional’ and ‘subjective/projective’ here. It is enough for our purposes that the “certain sorts” are, for Sider, ‘not objectively distinguished’ (p. 270). Or again in different words:

The core idea of the Humean account, then, is that necessary truths are truths of certain more or less arbitrarily selected kinds. (p. 271.)

At this point Sider introduces a refinement, and it is this that will allow us to see how Sider’s account embodies (Schema) above:

More carefully: begin with a set of modal axioms and a set of modal rules. Modal axioms are simply certain chosen true sentences; modal rules are certain chosen truth-preserving relations between sets of sentences and sentences. To any chosen modal axioms and rules there corresponds a set of modal theorems: the closure of the set of modal axioms under the rules.[footnote omitted] Any choice of modal axioms and modal rules, and thus of modal theorems, results in a version of Humeanism: to be necessary is to be a modal theorem thus understood.[footnote omitted] (“Modal” axioms, rules, and theorems are so-called because of their role in the Humean theory of modality, but the goal is to characterize them nonmodally; otherwise the theory would fail to be reductive. [...]) (p. 271.)

Then, getting more specific with a preliminary proposal:

A simple version of Humeanism to begin with: the sole modal rule is first‐order logical consequence, and the modal axioms are the mathematical truths. (Logical truths are logical consequences of any propositions whatsoever, and so do not need to be included as modal axioms.) (pp. 271 - 272.)

At this point, we can see how Sider’s account, or type of account, will embody (Schema); his notion of ‘modal axiom’ combines the requirements of truth and being of a “certain sort” (or one of “certain sorts”), and the main point of the ‘modal rules’ seems clearly to be to draw out implications of the axioms. So, separating the truth and “certain sort” requirements again, we can with little or no distortion put Sider’s preferred type of account into (Schema):

(SiderSchema) A proposition is necessary iff it is, or is implied by, a proposition which is both true and is of a more or less arbitrarily selected “certain sort”.

The presence in the account of implication (or something like it) is in my view an important and laudable feature. It is perhaps not sufficiently emphasized by Sider, and has been glossed over in subsequent discussion of his view. For instance, Merricks (2013) glosses Sider’s account as saying that ‘Sider reduces a proposition p’s being necessarily true to: p is true-and-mathematical or true-and-logical or true-and-metaphysical or…’. The importance of implication (or something like it) in (Schema) and views embodying it is made clear in my recent post on my account.

After giving his preliminary version of Humeanism, Sider goes on to consider a series of worries, responding with ‘a combination of refinement and argument’ (p. 272.) He never arrives at a definitive proposal, but aims to develop his strategy sufficiently to justify his general approach.

I think we have already gotten a pretty good sense of Sider’s approach, but I want more or less to complete the exposition of Sider’s approach before, in my next post, moving on to objections, none of which are among the worries Sider considers. So before moving on to objections, I will now briefly convey six further points which emerge in Sider’s responses to the worries.

1. Logical consequence must be non-modal: Sider wants his account to avoid modal notions, so modal characterizations of logical consequence are out. Remaining options include primitivism about logical consequence, something Sider calls the “best system” account of logical truth (which he describes in section 10.3 of his (2011)) extended to an account of logical consequence, and model theoretic approaches.
2. Analytic truths added as axioms: Sider holds that analytic truths should come out necessary, and proposes to that end that each analytic truth be added as a modal axiom (p. 274). This move is unapologetically ad hoc. (You might worry, as I do, that some examples of the contingent a priori should count as analytic, in which case not all analyticities are necessities. But perhaps there are different notions of analyticity which may give different results here. In any case let’s set this aside.)
3. “Metaphysical” statements added as axioms: again, modulo some fuzziness about what it takes for a statement to count as metaphysical - the gloss Sider uses is ‘truths about fundamental and abstract matters’ (p. 275) - true metaphysical statements are to be added as axioms. Again this is unapologetically ad hoc, or treated as a brute fact: ‘What justifies their status as modal axioms? This is just how the concept of necessity works. Such propositions have no further feature that explains their inclusion as modal axioms.’ (p. 275)
4. A new class of ‘natural kind axioms’: another unapologetically ad hoc addition, this time to accommodate the necessity of natural kind type examples of the necessary a posteriori, e.g. ‘Water is H20’. I refer the reader to (pp. 282 - 283) for details.
5. Contextual variation of the “outer modality”: it is conventional wisdom that modal talk in the wild should be understood as being about a contextually variable space of possibilities. This is often combined with a picture of an outer, unrestricted space of possibilities which does not vary. Sider suggests, as ‘more attractive’ (p. 281), that even the outer space is contextually variable - that ‘there can be contextual variation both in the modal axioms and the modal rules’ (p. 281).
6. Family resemblances (maybe): on (p. 288) Sider rehearses his (by now familiar) attitude to necessity thus: ‘Why are logical (or mathematical, or analytic, or …) truths necessary? The Humean’s answer is that this is just how our concept of necessity works.’ But then he turns around and suggests (pp. 288-289) that ‘a Humean need not be quite so flatfooted. [...] [The Humean] resists the idea that there is a single necessary and sufficient condition for being a modal axiom. Nevertheless, she is free to exhibit similarities between various modal axioms, just as one might exhibit similarities between things that fall under our concept of a game, to use Wittgenstein’s example. Doing this would help to show that the Humean concept of necessity is not utterly arbitrary or heterogeneous.’ This no doubt helps the plausibility of Sider’s account in a way, but may also play into the hands of an objector, as we shall soon see.

This completes our exposition of Sider’s theory. In the next post we will consider some objections.

References

Merricks, Trenton (2013). Three Comments on Writing the Book of the World. Analysis 73 (4):722-736.

Sider, Theodore (2003). Reductive theories of modality. In Michael J. Loux & Dean W. Zimmerman

Sider, Theodore (2011). Writing the Book of the World. Oxford University Press.

(eds.), The Oxford Handbook of Metaphysics. Oxford University Press 180-208.

Sider, Theodore (2013). Symposium on Writing the Book of the World. Analysis 73 (4):751-770.

Indicative Modality is Not Epistemic

Philosophers today frequently identify indicative modality with apriority, or at least identify it as an epistemic notion.

For instance, the abstract for a recent talk by Greg Restall (currently available at his website) refers to 'subjunctive (metaphyisical) and indicative (epistemic) modalities'.

Even Chalmers in his admirable piece on the tyranny of the subjunctive, which might be expected to resist this tendency, bites the bullet here. Witness:

(4) SIX POSSIBLE REASONS FOR FAVORING THE SUBJUNCTIVE 

(a) Indicative necessity is "merely epistemic".

[Answer: So? Before 1970, almost everyone thought necessity was tied to the epistemic (cf. Pap's book). Kripke *argued* that necessity and epistemic notions came apart, by appeal to the subjunctive, but one can't simply presuppose it.]

This is a mistake. Indicative modality is not epistemic. A proposition is subjunctively necessarily true when it could not have been false, no matter what. A proposition is indicatively necessarily true when it cannot be false, no matter what.

I see no reason to think we need to understand this latter notion by appealing to anything to do with knowledge or a knowing subject. The idea is rather that an indicatively necessary proposition is true by its very nature, or has truth as an internal property.

It may be that a proposition is a priori iff it is indicatively necessary (or maybe the two categories are almost but not completely aligned). I once proposed something like this as an analysis of the concept of apriority. While this may still be an instructive result, shedding light on apriority and indicative necessity both, I no longer think it should be thought of as giving the content or intension of the notion of apriority. That should be left as a concept which has to do with knowledge or knowability, and indicative necessity recognized as an interesting, and non-epistemic, concept in its own right.

This point is just a continuation of Kripke's work in distinguishing concepts of propositional typology which have typically been conflated.

Does Kripke Really Have Obstinate Rigidity in Mind at All in Naming and Necessity?

Philosophers, in the wake of Naming and Necessity, have distinguished the main Kripkean notion of rigid designation, which applies to an expression when it designates the same object in all possible worlds (or counterfactual situations) in which that object exists, from a putative notion called 'obstinate rigidity', which applies to an expression when it designated the same object in every possible world whatever, including worlds where that object doesn't exist. (The term 'obstinate rigidity' was introduced by Nathan Salmon on page 34 of his 1981 book, Reference and Essence.)

I'm not even sure I can make sense of the notion of obstinate rigidity. My main purpose here is not to discredit it, however, but to do something more modest: I want to suggest that a line of interpretation of Kripke, which has him sometimes working with a notion of obstinate rigidity instead of his normal official notion of rigidity, is mistaken.

From the Stanford Encyclopedia of Philosophy article 'Rigid Designators':

In other places, Kripke seems to have in mind another account of rigidity: one according to which a rigid designator designates its object in every possible world, whether or not the designatum exists in that world. Hence, he says, “If you say, ‘suppose Hitler had never been born’ then ‘Hitler’ refers here, still rigidly, to something that would not exist in the counterfactual situation described” (Kripke 1980, p. 78).

The interpretative suggestion before the quote seems wrong to me. I find it more natural to think that Kripke is saying that 'Hitler' actually refers, rigidly, to something that would not exist in another counterfactual situation - not that it refers to that thing in that situation.

Here we have to be careful to distinguish:

What does expression X refer to in counterfactual situation Y? (Which in turn must be carefully disambiguated, in a familiar Kripkean way, so that it does not get interpreted as asking about how language would be used in counterfactual situation Y.)

from

What does expression X actually refer to when it appears in this description of counterfactual situation Y?

You can answer 'Nothing' to the first and 'Hitler' to the second.

(Things may get even subtler when you consider definite descriptions. Suppose John is the tallest man in the world, but Paul might have been. Then if we say 'Paul might have been the tallest man in the world', should we still say that the actual referent of 'the tallest man in the world' in that sentence is John? To this, one wants to object that John isn't really involved. (But does that matter, when the question was about what the actual referent is?) Perhaps someone could find principled grounds for denying 'The actual referent of "the tallest man in the world" in that sentence is John' while accepting the 'Nothing'/'Hitler' pair of answers above. Perhaps Donnellan's distinction between referential and attributive uses of definite descriptions, or something like that distinction, should come into play here. Still, this complication - and it really is enough to do your head in - shouldn't impinge on the plausibility of what was said above.)

The Humphrey Objection to Modal Realism

The Humphrey objection to modal realism, due to Kripke, centres on counterpart theory, and alleges that this assigns counterintuitive truth-conditions to modal statements about individuals. It is historically important, as Kripke made the objection in his influential Naming and Necessity lectures, long before Lewis published his full defence of modal realism in 1986.

Kripke put the objection as follows:

Thus if we say "Humphrey might have won the election (if only he had done such-and-such)”, we are not talking about something that might have happened to Humphrey but to someone else, a "counterpart". Probably, however, Humphrey could not care less whether someone else, no matter how much resembling him, would have been victorious in another possible world. Thus, Lewis's view seems to me even more bizarre than the usual notions of transworld identification that it replaces. (Kripke 1980:45 note 13.)

It is by now, I think, pretty widely accepted that Kripke, while he may have been on to something here, did not put the point optimally. To the objection put this way, there is a cogent response: it is not correct to say that, according to counterpart-theoretic modal realism, we 'are not talking about something that might have happened to Humphrey'. What counterpart-theoretic says is that talk about 'what might have happened to Humphrey' is to be analyzed in terms of what does happen to his counterparts in other worlds. So according to the counterpart-theoretic modal realist, when we say 'Humphrey might have won the election', we are indeed talking about what might have happened to Humphrey. Their characteristic claim is to add that this thing we're talking about is to be analyzed in terms of what happens to counterparts. (Lewis drives this point home in On the Plurality of Worlds.)

Similarly, the second part of Kripke's objection – that 'Humphrey could not care less whether someone else, no matter how much resembling him, would have been victorious in another possible world' – can be convincingly argued to miss the mark. The counterpart-theoretic modal realist can agree that Humphrey could not care less about this. For the way they analyze talk about whether 'someone else' (a counterpart) 'would have been victorious in another possible world' is in terms of counterparts of that someone else – counterparts of Humphrey's counterparts. And it is compatible with Humphrey not being interested in what happens to the counterparts of some one of his counterparts, that he be interested in something which – upon analysis – turns out to be a question of what happens to his own counterparts.

This last point may be a bit pedantic, however. What if we simply reform the second part of Kripke's objection by changing the 'would have been' to an 'is'? This yields: 'Humphrey could not care less whether someone else, no matter how much resembling him, is victorious in another possible world?'

This is better, but there is still a strong reply. As Sider says in his unpublished 'Beyond the Humphrey Objection', this is 'just the paradox of analysis':

A reasonable person can care about a property under one description (“possibly winning”) while not caring about the same property under another description (“having a counterpart who wins”), provided it is not obvious that the descriptions pick out the same property. Correct analyses need not be obvious to competent language users. Obviousness may count for something, but theoretical virtues are important as well in determining which analyses we ought to accept (p. 2)

I endorse this as a response to the version of the Humphrey objection just considered. However, I want presently to register a difference with Sider about whether this response also works for another version of the objection.

This other version puts aside what Humphrey cares about, and appeals directly to our intuitions. Sider puts this version of the objection as follows: 'Look, it is just obvious that possibly winning is not the same as having a counterpart who wins' (pp. 1 – 2) And the response quoted above is put forward by Sider as a response to both the previously considered version and this one. (He explicitly prefaces the passage with 'Reply to ii) and iii)' (p. 2).)

Does Sider's response apply here too? On reflection, I think clearly not. The response makes the point that a correct analysis need not be obvious (while granting that obviousness may count for something). But the present version of the objection is alleging, not that it isn't obvious, but that it is obviously not the case. Sider, in putting the passage in question forward as a response to this, is sliding from '(~p) is obvious' to '~(p is obvious)' and thus failing to address the objection.

So we seem to have a version of the Humphrey objection which is stronger than the others so far considered. But we can improve it further by getting away from obviousness altogether, which is a red herring. Saying that possibly winning is obviously not the same as having a winning counterpart risks being too strong. The rhetorically wise thing to do is tone it down, and simply enter a plea that it doesn't intuitively seem that possibly winning is the same as having a winning counterpart. Or putting the point semantically: the truth-condition Lewis assigns to 'Humphrey could have won' is counterintuitive.

So, despite the availability of strong responses to the original and certain subsequent versions of the Humphrey objection, the core point remains that the truth-condition assigned by Lewis is counterintuitive.

(Incidentally, Lewis suggested that forms of ersatzism are no better on this score: in that case, what “gets into the act” is not another person, but 'some abstract whatnot' (Lewis 1986, p. 194.) This isn't a strong reply to the objection, of course, as ersatzism is far from the only other game in town when it comes to the semantics of modal attributions such as 'Humphrey might have won'. Nevertheless and for what it's worth: perhaps an abstract whatnot getting into the act is, from an intuitive point of view, not quite as bad as another person getting into the act. Bringing in another person, it seems to me, feels more like crowding out Humphrey, more like putting something in his place.)

So, there is a version of the Humphrey objection which has some force. However, modal realism with overlap, in contrast to counterpart-theoretic modal realism a la Lewis, is immune to the Humphrey objection. Lewis wasn't swayed by this, since he had reasons to think modal realism with overlap unpalatable. Since then, advocates of overlap have, as might have been predicted, emerged (most notably McDaniel in his (2004), 'Modal Realism with Overlap').

It may be that the considerations against overlap are quite compelling, in which case these together with the Humphrey objection (once it is freed from its initial faulty formulation) have significant force against modal realism in general. However, I do not want to get deep into comparing the relative merits of counterpart-theoretic modal realism and modal realism with overlap, and would prefer to have an objection along similar lines which applies to both. Therefore, I advocate that we take the Humphrey objection, not just as a self-sufficient objection which affects the dominant form of modal realism but not modal realism with overlap, but also as a clue: modal realism – in both flavours – may be counterintuitive on the semantic front, and this may be a good reason to reject it. Since the Humphrey objection itself fails to apply to modal realism with overlap, we should set it aside and go on to try for a more general semantic objection. I hope to develop this in a future post.

References

Kripke, Saul A. (1980). Naming and Necessity. Harvard University Press.

Lewis, David K. (1986). On the Plurality of Worlds. Blackwell Publishers.

McDaniel, Kris (2004). Modal realism with overlap. Australasian Journal of Philosophy 82 (1):137 – 152.

Sider, Theodore. unpublished. Beyond the Humphrey Objection.

Quine's Poor Tom Revisited: Against Sayward

UPDATE (Nov 2019): I have recently published a paper on this topic, 'Quine's Poor Tom', in the European Journal of Analytic Philosophy.

I have recently come back to the argument in section 31 of Quine's Word and Object. In a post just over four years ago I criticized the argument for a use-mention shift with regard to a principle which, on an opaque reading of 'believes', is a reasonable thing to require of a good logician, but which, on a transparent reading of 'believes', is not a reasonable thing to require of a good logician.

In Quine's argument as he stated it, the principle is introduced in terms of belief in sentences, which all but forces an opaque reading. But then when it is applied in the argument, Quine has semantically descended to a 'believes that' construction, and applies the principle in such a way as would only be legitimate if it is given the transparent reading.

The principle as originally stated runs as follows:

(Acumen) [P]oor Tom, whatever his limitations regarding Latin literature and local philanthropies, is enough of a logician to believe a sentence of the form ‘δp = 1’ when and only when he believes the sentence represented by ‘p’. (Quine 1960, p. 148.)

In that-clause form it runs as follows:

(AmbigThatAcumen) Tom believes that δp = 1 when and only when Tom believes that p

(For the definition of the 'δp = 1' construction see my original post, but it can be read as 'The truth-value of "p" = 1' without going far wrong.)

Sleigh's (1966) objection makes the same point that I made towards the end of my original post, namely that the (AmbigThatAcumen) is only a reasonable assumption on an opaque reading, whereas its transparent reading is needed for the argument. He did not note that Quine's originally stating the principle in terms of belief in sentences all but forces us to give it an opaque reading at that point in the argument.

Widerker (1977) and Sayward (2007) criticized Sleigh's objection. I did not engage with these papers in my original post. In this post, I would like to refute Sayward's criticism. I think this can be done more or less conclusively.

Widerker's objection is less easily dealt with, and leads us into some interesting territory. I am currently working on a paper where I try to sort out the whole mess, and try to draw a metaphilosophical lesson.

One of the most important things I did not appreciate earlier is that Quine in his argument does give us what is needed for a good argument for his ultimate conclusion, namely that it will not do to treat belief transparently always. Once we see this, what is so objectionable about his argument may start to look more like a matter of presentation.

The way Quine presents things, I would like to say, is not perspicuous, and cultivates an air of paradox. (Quine makes it look like he has shown that if we treat belief transparently always, and if Tom has good logical acumen and believes one true thing and one false thing, then he believes everything.) I think this is philosophically bad, and so presumably did Sleigh. But it is interesting to note that what originally looked more like a dry, logical error (so to speak) may be more effectively criticized in this way - as a matter of non-perspicuous, philosophically bad presentation, rather than the commission of a definite logical error which flouts a principle we could get the supporter of Quine's argument to agree to. (Compare on the one hand the attempts of "cranks" to show that Cantor's diagonal proof was unsound, and on the other hand Wittgenstein's more sophisticated criticisms. I have blogged about this matter elsewhere.)

Sayward's criticism is simply that Sleigh has left it unargued that (AmbigThatAcumen) on its transparent reading is an unreasonable thing to require of  a logician - put differently, the criticism is that Sleigh has left it unargued that (AmbigThatAcumen) on its transparent reading does not express a form of logical acumen. He writes:

So if Sleigh’s point is to carry much weight it must take the form of a claim that no logical acumen, or at least none at all widely shared, is expressed by [(AmbigThatAcumen) read transparently]. But so far as I can see that simply goes unargued in his paper. Indeed, so far as I can see the paper contains no argument that the logical acumen to which Quine referred is not expressed by [(AmbigThatAcumen) read transparently]. It is simply and baldly asserted. (Sayward (2007), pp. 57 – 58.)

This objection can be convincingly rebutted. Firstly, it gets the dialectic wrong. Quine, for his argument to be plausible, needs his hypothesis about Tom's logical acumen plausibly to be about some genuine kind of logical acumen. I think it is perfectly fair to point out that this only seems to be so if we take the hypothesis opaquely, in which case it doesn't support the argument. This is already a good objection, in my judgement, without any further argument that it is not the case that (AmbigThatAcumen) read transparently – contrary to appearance – does express logical acumen after all.

Admittedly, this appearance may not be universal. This leads us to a second, stronger, point against Sayward's objection: Sleigh does give an argument that no logical acumen is expressed by the transparent reading! Sayward's claim that he does not do so is a sheer mistake. The argument comes at the end of Sleigh's note and runs as follows (except I have, for ease of reading, removed the subscript notation which he applies to singular terms to disambiguate between transparent and opaque, and simply put bracketed specifications of the intended reading next to 'believes' instead):

Obviously, (4') does not express the idea of Tom's acumen. Consider: 

(9) Tom believes [transparent] that [δp] = 1. 

and 

(10) Tom believes [opaque] that [2­ - 1] = 1. 

Given (10), (9) is true provided the sentence represented by 'p' is true. But we cannot infer from this that Tom believes the sentence represented by 'p' even if every singular term in 'p' is taken transparently and even if Tom is overflowing with logical acumen. (Sleigh 1966, p. 93.)

Clearly this is an argument, so Sayward is just wrong in saying that Sleigh doesn't offer one. I think it's a perfectly good argument, too – although I think it was unnecessary to make 'believes' in (10) opaque and (as I hope to make clear in the paper I am working on and perhaps a future post here) this makes Sleigh more vulnerable to Widerker's criticism.

Finally, I think we can give a more straightforward argument that the transparent reading does not express any sort of logical acumen. To rewrite the principle with an explicit disambiguation:

(TransparentThatAcumen) Tom believes [transparent] that δp = 1 when and only when he believes [transparent] that p.

Now, let us plug in some truth for 'p' which not everyone with logical acumen knows – say, 'Quine was born in 1908':

Tom believes [transparent] that δ(Quine was born in 1908) = 1 when and only when he believes [transparent] that Quine was born in 1908.

Now, substituting '1' for the co­extensive 'δ(Quine was born in 1908)', we get

Tom believes [transparent] that 1 = 1 when and only when he believes [transparent] that Quine was born in 1908.

This is plainly not something we should require of a reasoner. Using 'of' language to induce a transparent reading, so that the point reads more intuitively: a reasoner may not believe, of Quine, that he was born in 1908. They may not have any beliefs about Quine at all. Obviously, they should not in that case – by the 'only when', which is essential to Quine's argument – fail to believe, of 1, that it is equal to 1. But we obtained this wrong result just by substituting co-extensive terms in an instance of (TransparentThatAcumen). Therefore (TransparentThatAcumen) does not express any sort of logical acumen. Rather, it seems like something we definitely shouldn't conform to.

The above, I think, completely diffuses Sayward's criticism.

References

- Quine, W. V. (1960). Word and Object. The MIT Press.

- Charles Sayward (2007). Quine and his Critics on Truth-Functionality and Extensionality. Logic and Logical Philosophy 16:45-63.

- R. C. Sleigh (1966). A note on an argument of Quine's. Philosophical Studies 17 (6):91 - 93.

- David Widerker (1977). Epistemic opacity again. Philosophical Studies 32 (4):355 - 358. 

Modal Realism

This is just an expository post, but I hope to make some original points in subsequent posts which will consider objections to modal realism.

Central to modal realism are the Leibnizian biconditionals,

(Leib­NEC) A proposition is necessary iff it is true in all possible worlds.
(Leib­POSS) A proposition is possible iff it is true at some possible world.

These tie attributions of necessity and possibility to quantificational statements about possible worlds. Different philosophical accounts which use these sentences accounts differ over what sorts of things possible worlds are taken to be, and over the role given to the Leibnizian biconditionals. (With typical forms of modal fictionalism, the biconditionals are typically augmented with an 'According to F' operator, where 'F' names a fiction.) The distinctive marks of modal realism, setting it apart from other philosophical uses of the Leibnizian biconditionals, are that it takes possible worlds to be of the same kind as the actual, concrete world we live in, that it takes the Leibnizian biconditionals to be true all by themselves (no fiction operator required), and that it takes these to constitute analyses of the modal notions appearing on the left hand sides.

The chief proponent and developer of modal realism, David Lewis, intends it to be a reductive account of modality – so his theory of possible worlds must be spelled out non­modally. Accordingly, the 'possible' in 'possible world(s)' on the right hand sides of the biconditionals is not supposed to be taken as anything more than part of a conventional, historically familiar way of referring to the worlds which do the work in his account. 

Such is the theory of modal realism in broad outline. Its characteristic commitments may be summed up in one sentence as 'There are other worlds, and every way our world might have been is a way some world is' (cf. Lewis 1986, p. 2).

In future posts I want to consider some objections to modal realism, but first let us consider in a preliminary way three finer points about the theory.

One finer point concerns the individuation of worlds. As Lewis phrases the question, 'What makes  two things worldmates? How are the worlds demarcated one from another? Why don't all the possibilia comprise one big world? Or, at the other extreme, why isn't each possible neutrino a little world of its own?' (Lewis 1986, p.70). Lewis's answer to this is: spatiotemporal relatedness. '[W]henever two possible individuals are spatiotemporally related, they are worldmates. If there is any distance between them – be it great or small, spatial or temporal – they are parts of one single world.' (This gives rise to an objection – the island universes objection – based on the idea that we should not in our analysis of modality rule out the possibility of a world with multiple spatiotemporally unrelated “universes”. I will not consider this objection at length, but cf. Lewis 1986, p. 71, Bricker 2001 and Vacek 2013.)

The second finer point concerns the treatment of propositions about particular individuals, and how they are to be evaluated with respect to worlds other than our own (or more generally, worlds other than the one from which the propositions in question are being evaluated). To begin with, note that general statements pose no corresponding difficulty. Going along with the modal realist's doctrine that there are other worlds, a question like 'Is “All swans are white” true at all worlds?' seems to have a straightforward meaning (at least given the familiar point that we want to hold fixed the meaning of the sentence in question when evaluating the proposition with respect to other worlds). But if we ask 'Is “John is white” true at all worlds?', where John is some actual swan, the question arises: does John himself exist at any of the other worlds?

The two different answers we might give to this question correspond to different forms of modal realism. If we answer in the affirmative, we get what is called modal realism with overlap. If we answer in the negative, get what is called modal realism without overlap. The canonical form of modal realism, David Lewis's as developed in his (1986), is of the latter sort. In order to enable us to evaluate propositions about particular individuals with respect to other worlds in the framework of modal realism without overlap, Lewis developed a theory of counterparts. To evaluate 'John is white' at some world W, we as it were look at that world and select the closest counterpart to our this-­worldly swan John, and then consider whether that swan is white. If so, we say that 'John is white' is true at W. This approach has been felt to be damagingly counterintuitive, giving rise to an objection originated by Saul Kripke called the Humphrey objection, which we will consider in a futute post.

The third and final finer point I want to note concerns the issue of what, if anything, modal realism has to say about the extent or range of the worlds – what worlds are there, and what are they like? As Lewis saw the matter, it was incumbent on him to provide principles which so to speak “generate” sufficient worlds, so that there is one for every possibility. To this end he proposed a principle of recombination, but he admitted that this was inadequate (Lewis 1986, p. 92). More recently, it has been questioned whether any such principles are needed for the theory qua analysis of modality (cf. Cameron 2012).

Note that modal realism is obviously free of the chief defects of pre-Kripkean analyticity approaches – the modal realist analysis does not push us toward the conclusions, implausible ever since Kripke, that necessary truths are true in virtue of meaning, or that they are all a priori. This is one of the things which, together with the boldness and clearness (at least in a certain sense) of the theory, makes it such a serious contender given the present state of play.

In future posts I will consider objections to modal realism, some of which we have just alluded to. My ultimate conclusion will be that the most serious objections are very serious indeed, and devastating when taken together. (General methodological qualms about certainty in philosophy aside, I believe that the theory is certainly incorrect. But it is profoundly incorrect and cannot be discussed too carefully. This series of posts will necessarily fall short of plumbing the full depths of the matter.)

References

Bricker, Phillip (2001). Island Universes and the Analysis of Modality. In G. Preyer & F. Siebelt (eds.), Reality and Humean Supervenience: Essays on the Philosophy of David Lewis. Rowman and Littlefield.

Cameron, Ross P. (2012). Why Lewis's analysis of modality succeeds in its reductive ambitions. Philosophers' Imprint 12 (8).

Lewis, David K. (1986). On the Plurality of Worlds. Blackwell Publishers.

Vacek, M. (2013). Modal Realism and Philosophical Analysis: The Case of Island Universes FILOZOFIA 68, No 10, p. 868-876.