Category Archives: Counterfactuals

CEM journalism

Posted on November 5, 2007 | Leave a comment

The literature on the linguistics/philosophy interface on conditionals is full of excellent stuff. Here’s just one nice thing we get. (Directly drawn from a paper by von Fintel and Iatridou). Nothing here is due to me: but it’s something I want to put down so I don’t forget it, since it looks like it’ll be useful all over the place. Think of what follows as a bit of journalism.

Here’s a general puzzle for people who like “iffy” analyses of conditionals.

No student passes if they goof off.

The obvious first-pass regimentation is:

[No x: x is a student](if x goofs off, x passes)

But for a wide variety of accounts, this’ll give you the wrong truth-conditions. E.g. if you read “if” as a material conditional, you’ll get it coming out true if all the students goof and succeed! What is wanted, as Higgenbotham urges, is something with the effect:

[No x: x is a student](x goofs off and x passes)

This seems to suggest that under some embeddings “if” expresses conjunction! But that’s hardly what a believer in the iffness of if wants.

What the paper cited above notes is that so long as we’ve got CEM, we won’t go wrong. For [No x:Fx]Gx is equivalent to [All x:Fx]~Gx. And where G is the conditional “if x goofs off, x passes”, the negated conditional “not: if x goofs off, x passes” is equivalent to “if x goofs off, x doesn’t pass” if we have the relevant instance of conditional excluded middle. What we wind up with is an equivalence between the obvious first-pass regimentation and:

[All x: x is a student](if x goofs off, x won’t pass).

And this seems to get the right results. What it *doesn’t* automatically get us is an equivalence to the Higgenbotham regimentation in terms of a conjunction (nor with the Kratzer restrictor analysis). And maybe when we look at the data more generally, we’ll can get some traction on which of these theories best fits with usage.

Suppose we’re convinced by this that we need the relevant instances of CEM. There remains a question of *how* to secure these instances. The suggestion in the paper is that rules governing legitimate contexts for conditionals give us the result (paired with a contextually shifty strict conditional account of conditionals). An obvious alternative is to hard-wire in CEM into the semantics, as Stalnaker does. So unless you’re prepared (with von Fintel, Gillies et al) to defend in detail fine-tuned shiftiness of the contexts in which conditionals can be uttered then it looks like you should smile upon the Stalnaker analysis.

[Update: It’s interesting to think how this would look as an argument for (instances of) CEM.

Premise 1: The following are equivalent:
A. No student will pass if she goofs off
B. Every student will fail to pass if she goofs off

Premise 2: A and B can be regimented respectively as follows:
A*. [No x: student x](if x goofs off, x passes)
B*. [Every x: student x](if x goofs off, ~x passes)

Premise 3: [No x: Fx]Gx is equivalent to [Every x: Fx]~Gx

Premise 4: if [Every x: Fx]Hx is equivalent to [Every x: Fx]Ix, then Hx is equivalent to Ix.

We argue as follows. By an instance of premise 3, A* is equivalent to:

C*. [Every x: student x] not(if x goofs off, x passes)

But C* is equivalent to A*, which is equivalent to A (premise 2) which is equivalent to B (premise 1) which is equivalent to B* (premise 2). So C* is equivalent to B*.

But this equivalence is of the form of the antecedent of premise 4, so we get:

(Neg/Cond instances) ~(if x goofs off, x passes) iff if x goofs off, ~x passes.

And we quickly get from the law of excluded middle and a bit of logic:

(CEM instances) (if x goofs off, x passes) or (if x goofs off, ~ x passes). QED.

The present version is phrased in terms of indicative conditionals. But it looks like parallel arguments can be run for CEM for counterfactuals (Thanks to Richard Woodward for asking about this). For one of the controversial cases, for example, the basic premise will be that the following are equivalent:

D. No coin would have landed heads, if it had been flipped.
E. Every coin would have landed tails, if it had been flipped.

This looks pretty good, so the argument can run just as before.]

Must, Might and Moore.

Posted on November 5, 2007 | Leave a comment

I’ve just been enjoying reading a paper by Thony Gillies. One thing that’s very striking is the dilemma he poses—quite generally—for “iffy” accounts of “if” (i.e. accounts that see English “if” as expressing a sentential connective, pace Kratzer’s restrictor account).

The dilemma is constructed around finding a story that handles the interaction between modals and conditionals. The prima facie data is that the following pairs are equivalent:

If p, must be q
If p, q

and

If p, might be q
Might be (p&q)

The dilemma proceeds by first looking at whether you want to say that the modals scope over the conditional or vice versa, and then (on the view where the modal is wide-scoped) looking into the details of how the “if” is supposed to work and showing that one or other of the pairs come out inequivalent. The suggestion in the paper is if we have the right theory of context-shiftiness, and narrow-scope the modals, then we can be faithful to the data. I don’t want to take issue with that positive proposal. I’m just a bit worried about the alleged data itself.

It’s a really familiar tactic, when presented with a putative equivalence that causes trouble for your favourite theory, to say that the pairs aren’t equivalent at all, but can be “reasonably inferred” from each other (think of various ways of explaining away “or-to-if” inferences). But taken cold such pragmatic explanations can look a bit ad hoc.

So it’d be nice if we could find independent motivation for the inequivalence we need. In a related setting, Bob Stalnaker uses the acceptability of Moorean-patterns to do this job. To me, the Stalnaker point seems to bear directly on the Gillies dilemma above.

Before we even consider conditionals, notice that “p but it might be that not p” sounds terrible. Attractive story: this is because you shouldn’t assert something unless you know it to be true; and to say that p might not be the case is (inter alia) to deny you know it. One way of bringing out the pretty obviously pragmatic nature of the tension in uttering the conjunction here is to note that asserting the following sort of thing looks much much better:

it might be that not p; but I believe that p

(“I might miss the train; but I believe I’ll just make it”). The point is that whereas asserting “p” is appropriate only if you know that p, asserting “I believe that p” (arguably) is appropriate even if you know you don’t know it. So looking at these conjunctions and figuring out whether they sound “Moorean” seems like a nice way of filtering out some of the noise generated by knowledge-rules for assertion.

(I can sometimes still hear a little tension in the example: what are you doing believing that you’ll catch the train if you know you might not? But for me this goes away if we replace “I believe that” with “I’m confident that” (which still, in vanilla cases, gives you Moorean phenomena). I think in the examples to be given below, residual tension can be eliminated in the same way. The folks who work on norms of assertion I’m sure have explored this sort of territory lots.)

That’s the prototypical case. Let’s move on to examples where there are more moving parts. David Lewis famously alleged that the following pair are equivalent:

it’s not the case that: if were the case that p, it would have been that q
if were that p, it might have been that ~q

Stalnaker thinks that this is wrong, since instances of the following sound ok:

if it were that p, it might have been that not q; but I believe if it were that p it would have been that q.

Consider for example: “if I’d left only 5 mins to walk down the hill, (of course!) I might have missed the train; but I believe that, even if I’d only left 5 mins, I’d have caught it. ” That sounds totally fine to me. There’s a few decorations to that speech (“even” “of course” “only”). But I think the general pattern here is robust, once we fill in the background context. Stalnaker thinks this cuts against Lewis, since if mights and woulds were obvious contradictories, then the latter speech would be straightforwardly equivalent to something of the form “A and I don’t believe that A”. But things like that sounds terrible, in a way that the speech above doesn’t.

We find pretty much the same cases for “must” and indicative “if”.

It’s not true that if p, then it must be that q; but I believe that if p, q.

(“it’s not true that if Gerry is at the party, Jill must be too—Jill sometimes gets called away unexpectedly by her work. But nevertheless I believe that if Gerry’s there, Jill’s there.”). Again, this sounds ok to me; but if the bare conditional and the must-conditional were straightforwardly equivalent, surely this should sound terrible.

These sorts of patterns make me very suspicious of claims that “if p, must q” and “if p, q” are equivalent, just as the analogous patterns make me suspicious of the Lewis idea that “if p, might ~q” and “if p, q” are contradictories when the “if” is subjunctive. So I’m thinking the horns of Gillies’ dilemma aren’t equal: denying the must conditional/bare conditional equivalence is independently motivated.

None of this is meant to undermine the positive theory that Thony Gillies is presenting in the paper: his way of accounting for lots of the data looks super-interesting, and I’ve got no reason to suppose his positive story won’t have a story about everything I’ve said here. I’m just wondering whether the dilemma that frames the debate should suck us in.

Edgington vs. Stalnaker

Posted on October 12, 2007 | 2 comments

One of the things I’m thinking about at the moment is Stalnaker-esque treatments of indicative conditionals. Stalnaker’s story, roughly, is that indicative conditionals have almost exactly the same truth conditions as (on his theory) counterfactuals do. That is, A>B is true at w iff B is true at the nearest B-world to w. The difference comes only in the fine details about which worlds count as nearest. For counterfactuals, Stalnaker like Lewis thinks that some sort of similarity does the job. For indicatives, Stalnaker thinks that the nearness ordering is rooted in the same similarity metric, but distorted by the following overriding principle: if A and w are consistent with what we collectively presuppose, then the nearest A-worlds will also be consistent with what we collectively presuppose. In the jargon, all worlds outside the “context set” are pushed further out than they would be on the counterfactual ordering.

I’m interested in this sort of “push worlds” modal account of indicatives. (Others in a similar family include Daniel Nolan’s theory, whereby it’s knowledge that does the pushing rather than collective presuppositions). Lots of criticisms of Stalnaker’s theory don’t engage with the fine details of what he says about the closeness ordering, but more general aspects (e.g. its inability to sustain Adams’ thesis that the conditional probability is the probability of the conditional; its handling of Gibbard cases; its sensitivity to fine factors of conversational context). An exception, however, is an argument that Dorothy Edgington puts forward in her SEP survey article (which, by the way, I very much recommend!)

Here’s the case. Let’s suppose that Jill is uncertain how much fuel is in Jane’s car. The tank has a capacity for 100-miles’-worth, but Jill has no knowledge of what level it is at. Jane is
going to drive it until it runs out of fuel. For Jill, the probability of the car being driven for n miles, given that it’s driven for no more than fifty, is 1/50. (for n<51).

Suppose that in fact the tank is full. The most similar worlds to actuality, arguably, are those where the tank is 50 per cent full, and so where Jane drives 50 miles. The same goes for any world where the tank is more than 50 per cent full. So, if nearness of worlds is determined by similarity, the conditional is true as uttered at each of the worlds where the tank is more than 50 per cent full. So without knowing the details of the level of the tank, we should be at least 50 per cent confident that if it goes for under 50 miles, it’ll go for exactly 50 miles. But this seems all wrong. Varying the numbers we can make the case even worse: we should be almost sure of “If it goes for no more than 3 miles, it’ll go for exactly 3 miles”, even though we regard 3, 2, 1 as equiprobable fuel levels.

Of course, that’s only to take into account the comparative similarity of worlds in determining the ordering, and Stalnaker and Nolan have the distorting factor to appeal to: worlds that are incompatible with something we presuppose/know to be true, can be pushed further out. But it doesn’t seem in this case that anything relevant is being presupposed/known.

I don’t think this objection works. To see that something is going wrong, notice that the argument, if successful, would work against other theories too. Consider, for example, Stalnaker’s theory of the counterfactual conditional. Take the case as before, but suppose we’re a day later and Jill doesn’t know how far Jane drove. Consider the counterfactual “Had it stopped after no more than 50 miles, it’d have gone for exactly 50 miles”. By the previous reasoning, the most similar worlds to over-50 worlds are exactly-50 worlds; so we should be half confident of the truth of that conditional. Varying the numbers, we should be almost sure that “If it had gone no more than 3, it’d go exactly 3”, despite regarding the probabilities of 3, 2 and 1 as equally likely. But these all seem like bizarre results.

Moral: the counterfactual ordering of worlds isn’t fixed by the kind of similarity that Edgington appeals to: the sort of similarity whereby a world in which the car stops after 53 miles is more similar to one in which the car stops after 50 miles than one in which the car stops after 3 miles. Of course, in some sense (perhaps an “overall” sense) those similarity judgements are just right. But we know from the Fine/Bennett cases that the sense of similarity that supports the right counterfactual verdicts can’t be all in cases (those cases are ones concerning counterfactuals starting “if Nixon had pushed the nuclear button in the 70’s…” All-in similarity arguably says that closest such worlds are ones where no missiles are released, leading to the wrong results).

Spelling out what the right notion of similarity is is tricky. Lewis gave us one recipe. In effect, we look for a little miracle that’ll suffice to let the counterfactual world diverge from actual history to bring about the antecedent. Then we let events run on according to actual laws, and see what happens. So in worlds where the tank is full, say, let’s look for the little miracle required to to make it run for no more than 50 miles, and run things on. What are the plausible candidates? Perhaps Jane’s decides to take an extra journey yesterday, or forgets to fill up her car two days ago. Small miracles could suffice to get us into those sorts of worlds. But those sorts of divergences don’t really suggest that she’ll end up with exactly 50 miles worth of fuel in the tank, and so this approach undermines the case for “If were at most 50, then exactly 50” being true in antecedent-false worlds. (Which is a good thing!)

If that’s the right thing to say in the counterfactual case, the indicative case too will be sorted. For it’s designed to be a case where presuppositions/knowledge don’t have a relevant distorting effect. And so, once more, the case for “If the car goes for at most 50, then it’ll go for exactly 50” doesn’t work.

I think that the basic interest of push-worlds theories of indicatives like Stalnaker’s and Nolan’s is to connect up the counterfactual and indicative ordering: whether there’s anything informative to say about the counterfactual ordering of worlds itself is an entirely different matter. So if the glosses of the position lead to problems, it’s best to figure out whether the problems lie withthe gloss of the counterfactual ordering (which then should be assessed in connection with that familiar and worked through literature) or with the push-worlds maneuver itself (which has, I think, been less fully examined). I think Edgington’s objection is really connected with the first facet, and I’ve tried to say why I think a more detailed theory will make the problem dissolve. But even if it did turn out to be a problem, the push-worlds thesis itself is still standing.

(Incidentally, I do think Edgington’s setup (which she attributes to a student, James Studd) has wider interest. It looks to me like Jackson’s modal theory of counterfactuals, and Davis’ modal theory of indicatives, both deliver the wrong results in this case.)

[Actually, now I’ve written this out, it strikes me that maybe the anti-Stalnaker argument is fixable. The trick would be to specify the background state of the world to make the result for counterfactual probabilities seem plausible, but such that (given Jill’s ignorance of the background conditions) the indicative probabilities still seem wrong. So maybe the example is at least a recipe for a counterexample to Stalnaker, even if the original case is resistable as described.]

2 Comments

Posted in Counterfactuals, Indicative conditionals

Chances, counterfactuals and similarity

Posted on October 4, 2006 | 10 comments

A happy-making feature of today is that Philosophy and Phenomenological Research have just accepted my paper “Chances, Counterfactuals and Similarity”, which has been hanging around for absolutely ages, in part because I got a “revise and resubmit” just as I was finishing my thesis and starting my new job, and in part because I got so much great feedback from a referee that there was lots to think about.

The way I think about it, it is a paper in furtherance of the Lewisian project of reducing counterfactual facts to similarity-facts between worlds, which feeds into a general interest in what kinds of modal structure (cross-world identities, metrics and measures, stronger-than-modal relations etc) you need to appeal to for metaphysical purposes. Lewis has a distinctive project of trying to reduce all this apparent structure to the economical basis of de dicto modality — what’s true at this world or that — and (local) similarity facts. Counterpart theory is one element of this project: showing how cross-world identities might be replaced by similarity relations and de dicto modality. Another element is the reduction of counterfactuals to closeness of worlds, and closeness of worlds is ultimately cashed out in terms of one world’s fitting another’s laws, and there being large areas where the local facts in each world match exactly. Again, we find de dicto modality of worlds and local similarity at the base.

Lewis’s main development of this view looks at a special case, where the actual world is presupposed to have deterministic laws. But to be general (and presumably, to be applicable to the actual world!) we want to have an account that holds for the situation where the laws of nature are objective-chance-laws. Lewis does suggest a way of extending his account to the chancy case. It’s attacked by Hawthorne in a recent paper—ultimately successfully, I think. In any case, Lewis’s ideas in this area always looked (to me) like a bit of a patch-up job, so I suggest a more principled Lewisian treatment, which then avoids the Hawthorne-style objections to the Lewis original.

The basic thought (which I found in Adam Elga’s work on Humean laws of nature) is that “fitting” chancy laws of nature is not just a matter of not violating those laws. Rather, to fit a chancy law is to be objectively typical relative to the probability function those laws determine. Given this understanding, we can give a single Lewisian account of what comparative similarity of worlds amounts to, phrased in terms of fit. The ambition is that when you understand “fit” in the way appropriate to deterministic laws, you get Lewis’s original (unextended) account. And when you understand “fit” in the way I argue is appropriate to chancy laws, you get my revised suggestion. All very satisfying, if you can get it to work!

10 Comments

Posted in Counterfactuals, Laws, Probability

An argument for conditional excluded middle.

Posted on September 1, 2006 | 18 comments

Conditional excluded middle is the following schema:

if A, then C; or if A, then not C.

It’s disputed whether everyday conditionals do or should support this schema. Extant formal treatments of conditionals differ on this issue: the material conditional supports CEM; the strict conditional doesn’t; Stalnaker’s logic of conditionals does, Lewis’s logic of conditionals doesn’t.

Here’s one consideration in favour of CEM (inspired by Rosen’s “incompleteness puzzle” for modal fictionalism, which I was chatting to Richard Woodward about at the Lewis graduate conference that was held in Leeds yesterday).

Here’s the quick version:

Fictionalisms in metaphysics should be cashed out via the indicative conditional. But if fictionalism is true about any domain, then it’s true about some domain that suffers from “incompleteness” phenomena. Unless the indicative conditional in general is governed in general by CEM, then there’s no way to resist the claim that we get sentences which are neither hold nor fail to hold according to the fiction. But any such “local” instance of a failure of CEM will lead to a contradiction. So the indicative conditional in general is governed by CEM

Here it is in more detail:

(A) Fictionalism is the right analysis about at least some areas of discourse.

Suppose fictionalism is the right account of blurg-talk. So there is the blurg fiction (call it B). And something like the following is true: when I appear to utter , say “blurgs exist” what I’ve said is correct iff according to B, “blurgs exist”. A natural, though disputable, principle is the following.

(B) If fictionalism is the correct theory of blurg-talk, then the following schema holds for any sentence S within blurg-talk:

“S iff According to B, S”

(NB: read “iff” as material equivalence, in this case).

(C) The right way to understand “according to B, S” (at least in this context) is as the indicative conditional “if B, then S”.

Now suppose we had a failure of CEM for an indicative conditional featuring “B” in the antecedent and a sentence of blurg-talk, S, in the consequent. Then we’d have the following:

(1) ~(B>S)&~(B>~S) (supposition)

By (C), this means we have:

(2) ~(According to B, S) & ~(According to B, ~S).

By (B), ~(According to B, S) is materially equivalent to ~S. Hence we get:

(3) ~S&~~S

Contradiction. This is a reductio of (1), so we conclude that

(intermediate conclusion):
No matter which fictionalism we’re considering, CEM has no counterinstances with the relevant fiction as antecedent and a sentence of the discourse in question as consequent.

Moreover:

(D) the best explanation of (intermediate conclusion) is that CEM holds in general.

Why is this? Well, I can’t think of any other reason we’d get this result. The issue is that fictions are often apparently incomplete. Anna Karenina doesn’t explicitly tell us the exact population of Russia at the moment of Anna’s conception. Plurality of worlds is notoriously silent on what is the upper bound for the number of objects there could possibly be. Zermelo Fraenkel set-theory doesn’t prove or disprove the Generalized Continuum Hypothesis. I’m going to assume:

(E) whatever domain fictionalism is true of, it will suffer from incompleteness phenomena of the kind familiar from fictionalisms about possibilia, arithmetic etc.

Whenever we get such incompleteness phenomena, many have assumed, we get results such as the following:

~(According to AK, the population of Russia at Anna’s conception is n)
&~(According to AK, the population of Russia at Anna’s conception is ~n)

~(According to PW, there at most k many things in a world)
&~(According to PW, there are more than k many things in some world)

~(According to ZF, the GCH holds)
&~(According to ZF, the GCH fails to hold)

The only reason for resisting these very natural claims, especially when “According to” in the relevant cases is understood as an indicative conditional, is to endorse in those instances a general story about putative counterexamples to CEM. That’s why (D) seems true to me.

(The general story is due to Stalnaker; and in the instances at hand it will say that it is indeterminate whether or not e.g. “if PW is true, then there at most k many things in the world” is true; and also indeterminate whether its negation is true (explaining why we are compelled to reject both this sentence and its negation). Familiar logics for indeterminacy allow that p and q being indeterminate is compatible with “p or q” being determinately true. So the indeterminacy of “if B, S” and “if B, ~S” is compatible with the relevant instance of CEM “if B, S or if B, ~S” holding.)

Given (A-E), then, I think inference to the best explanation gives us CEM for the indicative conditional.

[Update: I cross-posted this both at Theories and Things and Metaphysical Values. Comment threads have been active so far at both places; so those interested might want to check out both threads. (Haven’t yet figured out whether this cross-posting is a good idea or not.)]

18 Comments

Posted in Counterfactuals, Indicative conditionals, Logic