Monday, February 12, 2007

Williamson On The Epistemology Of Modality

Chapter 5 of Tim Williamson's new book The Philosophy of Philosophy argues that modal knowledge is a species of counterfactual knowledge. Why should we believe this? The only reason offered is that there is a logical equivalence between modal claims and certain counterfactuals. In Williamson's words (p. 25):

"Given that the equivalences … are logically true, metaphysically modal thinking is logically equivalent to a special case of counterfactual thinking, and the epistemology of the former is tantamount to a special case of the epistemology of the latter."

But it does not follow from the bare fact that modal claims are logically equivalent to certain counterfactual claims that modal epistemology is tantamount to a special case of counterfactual epistemology. By analogy, it does not follow from the fact that that disjunctive propositions AvB are equivalent to negated conjunctive propositions ~(~A&~B) that the epistemology of disjunctive propositions is a special case of the epistemology of negated propositions. Nor does it follow from the fact that atomic propositions A are logically equivalent to conjunctive propositions A&A that the epistemology of atomic propositions is a special case of the epistemology of conjunctive propositions.

The equivalences cited by Williamson cannot by themselves establish that knowing certain counterfactuals is the way – or even our usual way – of knowing modal facts. At most, they might be taken to suggest that knowing the relevant counterfactuals is a way of knowing modal facts. I take it that epistemologists of modality are (rightly) more centrally interested in the question of how we do know about modality than in the question of how we might know about modality.

Moreover, without supplementation, flagging the mere existence of logical equivalences is not even to specify a way of coming to know about modality. We are left wondering what the supposed way of knowing is supposed to be like. Is it envisaged that we know the modal claims by first knowing the counterfactual claims and then deriving the modal claims which are equivalent to them? If so, it looks very unlikely that many of us are using this route to modal knowledge much of the time. Most people could not work through the relevant derivations if they tried, and even those who could certainly don't seem to be doing that kind of thing very often. On the other hand, if the envisaged route to modal knowledge does not go via derivation from the equivalent counterfactuals, what is it like? And what is the epistemological significance of the equivalence?


Joachim Horvath said...

One could see what Williamson is doing as a theoretical reconstruction of our entitlement for modal beliefs - even if it does not map nicely onto the psychological processes by which we usually acquire our modal beliefs (think about, for example, Boghossian's analyticity templates here!).

Alternatively, Williamson could take a more revisionist line by pointing out that our supposed knowledge of metaphysical modalities is entirely mysterious and could, therefore, only be obtained via empirically grounded counterfactuals. So, he could argue, his counterfactual way is the only plausible route to modal knowledge for human beings at all, and consequently, all other routes should be abandoned.

Andreas said...


I think the alternative route you suggest is entirely closed off to Williamson given that his claim is one about the methodology of using intuitions about metaphysical modalities in philosophy - cf. his discussion of the Gettier cases in ch. 6. These intuitions are standardly taken to gain access to a realm of a priori knowledge. As he sees it, there has traditionally been two opposing standpoints towards this kind of methodology, namely what he calls the 'crude rationalist' and the 'crude empiricist'. The former sees the intuitive, a priori methodology as a virtue, the latter sees it as vice. Williamson wants to claim that both are misguided since they share the common presupposition that the kind of reasoning in question is fundamentally detached from our ordinary, pretheoretical, ways of thinking. So, clearly he cannot claim that "knowledge of metaphysical modalities is entirely mysterious". Rather, this claim is exactly the one that he attributes to the tradition he wants to oppose.

I agree with Carrie that merely showing that A and B are logically equivalent does not show that the epistemology of A is tantamount to the epistemology of B (or indeed vice versa). Williamson definitely has more explaining to do.

Indeed, one might equally worry about the fact that the way in which Williamson attempts to achieve the logical equivalences in question, he is appealing to principles which are far from intuitively obvious, for instance vacuous truth for counterfactuals.

Joachim Horvath said...


surely my way of putting the alternative was quite elliptic. So, what I meant by saying "our supposed knowledge of metaphysical modalities is entirely mysterious" was of course intended to capture the spirit of Williamson's critique of "crude rationalism" - not his own attitude towards modal knowledge per se. Also, I'm not sure if Williamson really couldn't take my alternative, revisionist route. After all, it would still afford knowledge of metaphysical modalities - it only suggests an alternative way of getting there.

Andreas said...

Hi Joachim,

It is definitely interesting to ask whether Williamson would agree that if it hadn't been for our competence with the special cases of the counterfactual, then we wouldn't have had any modal knowledge at all. If I've understood you correctly, this would be the line taken by your revisionist.

However, I don't think Williamson would agree to this. I think his view is that the statement that p is necessarily true makes the same claim as the statement that no matter what would have been the case, p would have been the case.

So, Williamson's position is not that modal knowledge is something we have to reach - and that the counterfactual route is one, or perhaps the only, way of getting there. The claim is that knowledge of metaphysical modalities just is knowledge of these special instances of the counterfactual.

Joachim Horvath said...

Hi Andreas,

if your exegetical point about Williamson is right, then Carrie's point applies with full force - because, for example, the mental state of knowing that p just isn't the same mental state as knowing that ~~p. So, knowing the counterfactual and knowing the equivalent necessity aren't the same state of knowledge, either. Here, I guess, my first option might seem attractive: viewing Williamson's proposal as a rational reconstruction of our epistemic entitlement, regardless of our actual psychological processes or states.

By the way, the reason why I was talking about a "counterfactual route to modal knowledge" is the following: Williamson proposes a way to gain quasi-empirical knowledge of counterfactuals (by an "off-line" use of our percepual capacities, i.e. by some kind of mental simulation), yet no direct way to get knowledge of necessities. So at least it looks like he has something like a route from counterfactual to modal knowledge in mind.

Andreas said...

Hi Joachim,

Yeah, I agree with this. As I said in my first comment, I think Carrie is right to point out that logical equivalence, even if it is genuine (whatever that means), does not imply epistemological equivalence.

I just think it is crucial to see that Williamson is not making any kind of reductionist claims. He merely takes what at first glance looks like two spheres of our cognitive lives and argues that they are really one and the same.

As I've also indicated, I don't think that this move is unproblematic at all.

(Sorry if I misunderstood your point to begin with.)

Joe Salerno said...

Hi Carrie,

I think we need to read Williamson as offering an account of how modal knowledge is possible for beings like us, and not as defending the empirical thesis that our modal knowledge in fact depends on counterfactual knowledge. Whether or not our knowledge of necessity and possibility does (or must) take a detour through counterfactual is not TWs focus (as I see it). The epistemological claim is that beings like us, who are in a position to know the right-hand side of the equivalences, are (in virtue of the equivalence) also in a position to know the modality on the left-hand side.

I say a little more over at Knowability.