I'm now starting to shift back into research mode, however, and blog activity may come back up accordingly.
One of the philosophy books that has been on my 'to-read' list for a long time is Jessica Brown's Anti-Individualism and Knowledge; I've been interested in the relationship between mental content and epistemology for a while now. Of course if I'd been cleverer about it, I'd've read the book while I worked at St Andrews and spoke to Jessica regularly, but: better late than never.
Among the interesting things Jessica is up to in her book is an argument that Fregeanism about content is inconsistent with -- or at least, fits poorly with -- anti-individualism. This is the negation of one of the chapters of The Rules of Thought, so I wanted to attend especially to the argument. (Thanks to Sandy Goldberg for bringing this connection to my attention recently.)
One of Jessica's arguments boils down to this. (I'm looking at pp. 200-201.)
- Fregean sense depends for its motivation on the transparency of sameness of mental content.
- Anti-individualism is inconsistent with the transparency of sameness of mental content.
- Therefore, if anti-individualism is true, then Fregean sense is unmotivated.
In defense of (1), Jessica suggests that, were it possible for a subject to be wrong about whether two token concepts express the same content, the failure to make logically valid inferences would be consistent with full rationality. Celeste is in a Frege case.
Celeste fails to make the simple valid inference ... since she does not realize that the relevant thought constituents have the same content and thus that the inference is valid. Further, she can come to the correct view only by using empirical information. On this view, her failure to make the simple valid inference does not impugn her rationality, for even a rational subject would fail to make a valid inference that she does not realize is valid.
Jessica suggests that Fregeanism is motivated by the possibility of rationally holding what would be according to non-Fregean views contradictory sets of beliefs, or rationally declining to infer according to what such views would say are logically valid inferences. I agree -- a central motivation for Fregeanism is to explain why there's nothing irrational about believing Hesperus to be F and believing Phosphorus not to be F. But why does this rely on the assumption of the transparency of sameness of content? Jessica says in the passage above that there is an alternate explanation available, if transparency is denied: one doesn't make what is in fact a logically valid inference because one doesn't realize that it is valid, and this is consistent with full rationality.
Jessica's argument seems to rely on this claim:
(Reflection) If a subject doesn't realize that an inference is valid, then she faces no rational pressure to make it.
But Reflection strikes me as a pretty dubious principle in generality. Suppose somebody is pretty dense, and fails to realize that modus tollens is a valid inference form, and so fails to realize that various instances of it are valid. She sits there and thinks if it has an even number, then it's red and it's not red, and finds herself with no inclination to infer it has no even number. Surely her ignorance doesn't excuse her rational failure. So Reflection is false in generality; so arguments that rely on Reflection are unsound. It looks to me like Jessica is relying on Reflection, so I think her argument is unsound.
That said, there is admittedly an intuitive difference between my dense character and Jessica's ignorant one -- Jessica's character's failure to infer in accordance with valid inferences would be corrected by suitable empirical information; mine presumably wouldn't. Could this motivate a weakening of Reflection to render Jessica's verdict while avoiding the problematic one? Maybe, but it looks to me like it'd end up pretty ad hoc. (One upshot of Timothy Williamson's work on apriority is that it's very difficult precisely to state the kinds of connections to empirical investigation that underwrite certain intuitions.)
The Fregean can say this: failure to infer according to logically valid inferences is a rational failure, whether or not the subject recognizes the inference as a logically valid one. This, combined with the intuitive verdicts (no rational failure) about Frege puzzle cases, implies Fregeanism, but does not require any thesis about the transparency of content. This seems to be to be the natural thing to say.
Edit: Aidan McGlynn tells me that John Campbell and Mark Sainsbury are on the record against (1) in Campbell's 'Is Sense Transparent?' and Sainsbury's is 'Fregean Sense' in his collection Departing From Frege. I'll be interested to read them.