Stalnaker on Lewis on Intentionality
Stalnaker's "Lewis on Intentionality" (AJP 82, 2004) is a very odd paper. The aim of the paper is to show that Lewis's account of intentional content as developed in "Putnam's Paradox" -- global discriptivism with naturalness constraints -- faces various problems and conficts with what Lewis says elsewhere.
The first thing that's odd about this is that in "Putnam's Paradox", Lewis doesn't develop an account of intentional content. Rather, he discusses Putnam's model-theoretic argument and suggests that if one holds something like global descriptivism about linguistic content, adding external naturalness constraints on the interpretation of predicates would be an attractive way to block Putnam's argument for underdetermination.
As I've mentioned previously, it is clear from Lewis's many writings on the philosophy of language -- like Convention, "Languages and Language" and On the Plurality of Worlds, pp.40--50 -- that global descriptivism (with or without naturalness constraints) is not Lewis's own account of linguistic content. On Lewis's account, the correct interpretation of our sentences is not determined by what makes some set of sentences true, but rather by the behaviour, expectations and intentions of the relevant community. Assigning the proposition that there are cats to the English sentence "there are cherries" is ruled out simply because it doesn't fit our usage. Thus Lewis notes at the beginning of "Putnam's Paradox" (pp.57f. in Papers),
I shall acquiesce in Putnam's linguistic turn: I shall discuss the semantic interpretation of language rather than the assignment of content to attitudes, thus ignoring the possibility that the latter settles the formes [as Lewis himself believes]. It would be better, I think, to start with the attitudes and go on to language. But I think that would relocate, rather than avoid, the problem; wherefore I may as well discuss it on Putnam's own terms.
Apparently, Stalnaker read this passage -- the only place in "Putnam's Paradox" where Lewis mentions the interpretation of mental states -- as saying that the account of linguistic content to be sketched later in the paper is really meant to apply to mental content. But Lewis doesn't say that. He only says that Putnam's underdetermination problem also applies to the interpretation of mental states. The last remark in the quoted text also indicates that Lewis thinks the solution will be similar in both cases. The solution suggested in "Putnam's Paradox" is to employ objective naturalness as a constraint on correct interpretations. And indeed he also employs such a constraint on the interpretation of intentional states. But it is certainly odd to infer that Lewis intended all his later remarks on linguistic content -- the descriptivist framework; the rejection of external causal constraints on reference; etc. -- to carry over to the interpretation of intentional states. Even stranger is it to say, like Stalnaker, that Lewis here develops his account of intentional content.
Stalnaker's interpretation is particularly odd because Lewis has extensively written about his views on mental content, e.g. in "Radical Interpretation", "Veridical Halluzination and Prosthetic Vision", On the plurality of worlds pp.27-40, "Reduction of Mind", and elsewhere. And even more than in the case of his theory of language, it is plain that the account of intentional content developed in these writings bears little resemblance to global descriptivism. Stalnaker himself notes that if there is no language of thought, which Lewis took to be an open question, it's hard to see how the interpretation of mental states could proceed by ramsification of mental sentences and by assigning natural classes to mental predicates. But he takes that to be a problem for Lewis, rather than a problem for his understanding of Lewis.
As indicated in "Putnam's Paradox", Lewis also sees an underdetermination problem for intentional content, and again he appeals to naturalness constraints to rule out deviant interpretations. But for mental content, he also employs various other constraints, among them causal ones: the contribution of perceptions to belief content is fixed mainly by the phenomena that cause the perception.
Stalnaker notes this as well, and suggests (on p.206) that in "Putnam's Paradox", Lewis took back the causal constraint in favour of causal descriptivism, i.e. in favour of adding the constraint as a clause into the theory under consideration. But firstly, Lewis uses the external causal constraint in "New Work for a Theory of Universals" (p.50 in Papers) and On the Plurality of Worlds, which appeared shortly before and shortly after "Putnam's Paradox", respectively, and he still uses it much later, e.g. in "Reduction of Mind" (1994) and "Naming the Colours" (1998). So at best one could claim that for a very short period of time around 1984 -- a period in which he wrote virtually nothing on intentional content --, Lewis briefly jettisoned a major part of his account, without anywhere pointing out this radical change of view.
Secondly, what would it actually mean to replace Lewis's causal constraint on intentional content by a further clause in "the theory"? Presumably it would mean that when interpreting intentional states, we shouldn't assume that persons usually form true beliefs about the observable features of their surroundings, but only that they believe that persons usually form true beliefs about the observable features of their surroundings. It's hard to see how this peculiar view could be motivated by anything like the (very good) reasons that favour causal descriptivism about names over the causal theory of reference.
Finally, there's no need to speculate what Lewis might have had in mind when he said, in the passage quoted from "Putnam's Paradox", that the underdetermination problem also (or rather, mainly) applies to mental content, and how he thought the solution for the relocated problem would look like. In a footnote to the quoted passage he writes:
For a discussion of the 'relocated' problem and its solution, see the final section of my 'New Work for a Theory of Universals' [...].
Looking at that section, we find the very same non-descriptivist account of intentional content Lewis puts forward in all other places, including the external causal constraints (there called "principles of fit on the input side").
So Stalnaker assumes that Lewis develops an account of intentional content in a paper that doesn't discuss intentional content at all; and that this account is Lewis's own preferred account, despite the fact that it contradicts all his numerous earlier and later writings on intentional content, including the presentation to which readers interested in intentionality are directed in the paper where the account is allegedly developed.
Odd, isn't it?