Lewis defends a kind of best system theory both with respect to laws of nature and with respect to mental content: something is a law of nature iff (roughly) it is part of the best theory about our world; somebody believes that snow is white iff (roughly) this is what best makes sense of his behaviour according to our belief-desire psychology.
In both cases, it looks on first sight as if the theory introduces an implausible relativity into its subject matter: We don't want to say that the laws of nature depend on what we happen to find simple (but simplicity is part of what makes a theory good), and we don't want to say that what someone believes and fears depends on what we think about his behaviour.
On page 305 of "Assertion Revisited" (in the latest issue of Phil.Studies), Robert Stalnaker suggests that the information conveyed by an utterance is the diagonal proposition associated with the utterance iff it is unclear in the relevant context which horizontal proposition the utterance expresses:
[T]he relevant maxim is that speakers presume that their addressees understand what they are saying. In terms of the two-dimensional apparatus, this presumption will be satisfied if and only if the propositional concept for the utterance [a function that assigns to every relevant possible context the horizontal proposition expressed by the utterance in that context] is constant, relative to the possible worlds that are compatible with the context. Our problematic example [of saying "Hesperus is Phosphorus" to O'Leary who doesn't yet know that Hesperus is Phosphorus], and all cases of necessary truths that would be informative (in the sense that the addressee does not already know that they are true) will be prima facie counterexamples to this maxim, and so will require reinterpretation [so that what is said is the diagonal, not the horizontal proposition].
Three comments:
I'm busy with lots of other things. Blogging will probably resume sometime next week.
(This is a follow-up to the previous post.) I think I've found a better way to provide for things like population-dependence in a Lewisian semantic framework. The trick is to regard it as a kind of index-dependence without explicitly introducing population-coordinates into the indices.
Recall, we want "pain*" to denote whatever state occupies the pain-role in the relevant population. Unfortunately, the relevant population isn't just the most salient population in the context of utterance, for we want to say things like
This is going to get a bit weird and technical. I wonder how a Lewisian semantics (along the lines of "Index, Context and Content" and "General Semantics") for terms like "pain" can make true everything Lewis says about such terms.
Assume that
1) Necessarily, for all x, x is in pain* iff x is in a state that plays the pain-role in normal members of the kind to which x belongs.
By "the pain-role" I mean the causal role attributed to pain by folk psychology. By "pain*" I mean whatever satisfies the condition expressed by (1). So (1) is more like a definition than an assumption. Lewis believes that our ordinary concept of pain roughly satisfies (1), but for what follows this doesn't matter. I think it's clear that we could have concepts for which something like (1) holds. Lewis's example of having a certain number stored in memory, as denoting a state of pocket calculators, sounds plausible to me (with the pain-role replaced by the role attributed to the state of having a certain number stored in memory by folk pocket calculator theory).
This comment by Gideon Rosen in the fascinating thread on IR at TAR made me smile:
Consider two opinionated journalistic essays on the same controversial topic ? say, the morality of Sharon-style extra-judicial killing, and suppose it's clear that both writers agree on the underlying facts. One says that the killings are unjustified because they violate a fundmental moral right to due process. The other says that there is natural rights are nonsense on stilts and that the killings are justified because they maximize utility. [...]
According to the Lewis-Nemirow ability hypothesis, knowing what it's like to see red is having a certain cluster of abilities. According to almost everybody who writes about the ability hypothesis, the hypothesis also claims that knowing what it's like neither is nor involves any kind of knowledge-that. This is indeed suggested by some of Lewis' remarks, in particular by this one on p.288 of "What Experience Teaches" (in Papers):
The Ability Hypothesis says that knowing what an experience is like just is the possession of [...] abilities to remember, imagine, and recognize. It isn't the possession of any kind of information, ordinary or peculiar.
One has to read the rest of the paper to find out that by "information", Lewis here most probably means exclusion of possible worlds. At any rate, it is clear from the rest of the paper that Lewis doesn't claim that all Mary learns are abilities.
I haven't really checked the literature, but is there a general agreement on why the problem of temporary intrinsics is a problem of intrinsics and not a general problem about temporary properties? Certainly it is just as impossible for a thing both to have and to lack an extrinsic property as it is impossible for intrinsic properties. A while ago, I said that perhaps for temporary extrinsics, the problem is not really a problem because the relational answer is the obviously correct one: having extrinsic property F at time t clearly means being F-related to t. But in fact that doesn't sound obvious at all. Does being an uncle relate people to times? It seems not. It seems only to relate them to other people. If one intuits that being round is not a relation to a time, I don't see why one wouldn't similarly intuit that being an uncle is not a relation to a time.
This argument is not deductively valid:
The best available theory says p;
Therefore, p.
For even the best available theory can be false. It's not even clear that the premiss makes the conclusion very probable. So is it fallacious to argue for a claim by pointing out that it is entailed by the best available theory? No. The argument may be valid in another sense: in the sense that it is irrational to accept the premiss but reject the conclusion. For if you accept that the best available theory says p, rejecting p means to knowingly reject the best available theory -- and that may well be irrational. It's always irrational to knowingly reject the best available theory in favour of another, worse, theory. The only rational alternative is agnosticism. But if the best theory is sufficiently good and much ahead of its rivals then agnosticism too is irrational. That's because rationality demands that you increase your credence in a proposition in the light of good reasons.
Via Brian, I came across the recent debate in JPhil on whether knowing-how entails knowing-that. Jason Stanley and Tim Williamson make a good case that it does, but Ian Rumfitt makes an even better case that this holds only for one of the two meanings of "knowing how", namely for the one that translates as "savoire comment [faire]" in French, but not for the one that translates as "savoire [faire]". The former provides by far the most natural interpretation (and translation into French) of "Alex knows how to get to the nearest place selling beer". So the fact that