Writing about...

Instead of blindly trying to edit my paper by asking myself if I agree with every individual sentence, I've decided to step back and remind myself what I'm trying to accomplish. This could get rocky!...Hang on!...

When we talk about the contents of a perceptual experience, we assign to it a kind of abstract entity, a function from situations to truth-values, which is very much like the kind of abstract entity we assign to a meaningful, well-formed sentence (occurring at a context). When we do this, we assign to perceptual experiences Lewis [1980]'s "first job" for semantic values: determining a truth-value at a context.

However, a big difference with giving semantics for sentences is immediately apparent: perceptual experiences don't have meaningful *parts.* So we cannot give ourselves the compositional project of accounting for the content of the whole experience in terms of the contents of the parts. There is no analogue, for theorizing about perceptual content, of the constraints that compositionality imposes on our semantic theorizing "from below": we just don't know what it would *mean* to give a theory of content for the whole of a perceptual experience by giving a theory of content for the experience's parts, because, er, experiences don't *have* parts in the same way that sentences do. Or at least, *if* they do, this would come as a big fat surprise to me.

We can say that the need for a compositional theory of language is grounded in the bald fact about our language that it consists of sentences which are s.t. the meaning of the whole supervenes on the meanings of the parts. Yet it is worth noting that this is not the way compositionality is usually argued for. The argument is usually put in terms of our *knowledge* of our language: we say that we need a compositional theory for our language because we observe that knowledge of the parts of a well-formed sentence is sufficient for knowledge of the meaning of a novel combination of those elements. (This is what Prof. Yalcin calls the "productivity" of our linguistic knowledge.) I am somewhat confused here as to whether there is a genuine difference in views; presumably our knowledge is productive because our language is productive, and our language is productive because our knowledge of it is productive. Perhaps there is no genuine difference here, just two different ways of putting the point. The first way is to make the compositionality of language sound like a *metaphysical* truth: the meaning of our language just *is* s.t. the meanings of whole sentences is determined on the meanings of their parts. Hence the meanings of the parts are metaphysically sufficient for determining the meanings of new wholes constructed out of those parts. The second way to look at it is as an *epistemic* truth: it turns out to be true of us that we can understand novel sentences whenever we have prior "acquaintance" with their parts. Hence, if we are giving a theory which is supposed to capture (not just the nature of our language but) the nature of OUR KNOWLEDGE of our language, the theory should account for this fact. It would be compatible with such a theory, and such an outlook on the constraint of compositionality, that other creatures with other epistemic habits could speak the SAME language as we do, yet not be "productive" consumers of the language in the same sense that we are. Is this really possible?...I am inclined to feel rather skeptical that this is possible. So to the extent that the two views of compositionality come apart, I am more sympathetic towards the "metaphysical" view.

We return to the nature of perceptual experiences, and the project of assigning them content. We have just come from the observation that we cannot go, as it were, below the level of the whole representational experience, to assign content to its proper parts (upon which the content of the whole will then metaphysically-cum-epistemically supervene.)* But that's okay...after all, that part of compositionality is not even what Lewis is interested in. He is interested in compositionality "from above": on the constraint imposed by the fact that well-formed sentences compose with sentential operators. The question becomes: what (how complex a) semantic value must we assign to the argument-sentence so that this semantic value is sufficient for determining the semantic value whole sentence? It turns out--famously...--that the semantic value must include things that are not in (and not recoverable from) the set of all contexts. This is the set of possible indices.

Now, the analogy I am pursuing in the paper, which is only a partial analogy, is this: although there are ALSO no "experience operators" around for philosophers of perception to talk about, there *is* something quite similar: there are distinct phenomenal states which the content of perceptual experience can interface with. One of these is imagination. Another is memory. Perhaps yet a further one is premonition...who knows?

What is this like, in the philosophy of language?
Well, it's really more like giving a theory of content for representational mental states, rather than sentences. One and the same content can be both believed and supposed (maybe entertained as possible, even, where this is a separate state.) We want to seek this thing, the content, which can be both believed and supposed, so that we intuitively get right what belief and supposition have in common and how they differ.

One oft-proposed connection between content qua representational mental states and philosophy of language is giving a semantic account of *what is said* (which might or might not be identical with giving a semantics for the verb "said that.") Roughly, the idea is that what you say expresses what you believe, and that is just the semantic value of your sentence evaluated at the context of your believing/uttering. The context will play two roles: it will initialize the index (to wit, it is the index of the context that will determine whether the sentence is true or false) and it will fix the extension of indexical terms.

Upshot: maybe our project is like giving an account of what is said/what is believed. What this means is that we may not need an index as well as a context.

Here are two arguments meant to push us to the "index too" conception:

1) Indexicals have semantic values which are sensitive to context. But indexicals don't shift in the scope of modal operators.

I don't think this consideration is relevant either to the language case OR (a fortiori...) to the representational state case. We could just say that indexicals are rigid designators. So while they're sensitive to context for their semantic values, the semantic values don't shift. This could be implemented in several ways. We could restrict the accessibility relation on other contexts. We could define an intermediate notion of 'contextual proposition', where all the values for the indexicals were fixed, and then quantify over whatever remained in the scope of the operator (this would be the equivalent of giving the indexicals widest scope.)

2) There are cases in which the compound sentence you get from intensional operator + sentence just doesn't seem to have the truth-conditions you would get if the intensional operator quantified over contexts. For example, "It might have been that I am not here now." That is true, even though "I am here now" is true in every context. This, it seems to me, is what genuinely makes the case for independently shiftable indices. Note that the argument will go through with an indexical-ridden sentence like "I am here now" even if we took the indexicals to be rigid designators across contexts: all this would mean is that in the scope of the modal operator, "I" always refers to the speaker of the original context, "here" always refers to the location of the original context, and "now" always refers to the time of the original context. In such a language, for example, "I might have been male" isn't made true because a man might have said it; the only contexts quantified over are contexts where the original speaker is still the speaker of the context. So "I might have been male" is false. Nontheless, "I might not have been here" is still true.

While I think this is the right argument for the language case, this argument does not generalize to the perception case, because as we said, there is no analogue of an intensional operator. So my verdict is that so far the "we must have index as well as context!" claim does not go through.

Could an argument from supposing, considered as an attitude taking a propositional complement, be sufficient to overthrow this conception?

...It might be, depending on what we take supposing to be. It seems that supposing can shift individual indices (= individual features of context). We can suppose that I am not here. (I do this all the time, by way of supposing I am elsewhere.) We can suppose it's raining but we don't believe it is. We can suppose that Hesperus is not Phosphorus, for that matter. We can suppose many things which are (i) not true in any context, and furthermore (ii) not true at any index (though we'll leave that one aside for now.) Perhaps this is identical with the attitude of pretense.

An argument that we need more than just contexts to represent the contents of our attitudes of supposing would have to proceed from a variation on the second type of argument. If it just seems like an appeal to intuition, that might be ok with me...it seems like a pretty *strong* appeal to intuition! It would just be to say: can you suppose you're not here? And the answer is just: yes. What is a bit unsatisfying about the dialectic of my paper is that this is precisely what my interlocutors deny. How to respond?...well, I guess my intuitive response is that they don't really believe this on the basis of intuition; they are in the grip of a theory. So the task shifts to explaining why the theory is wrong, which is sort of complicated. In that discussion, it seems like my initial advantage is somehow lost, for want of emphasis.

If we want to put non truth-apt supposings in the form of sentences with different truth values, the nearest analogue seems to be the antecedent of a conditional. Suppose p; is q true? This is just: is it true that p->q? So a way to show that you needed indices as well as contexts here would be to find two sentences p and q that did not differ in their truth-at-a-context profile: whenever p is true at a context, q is true at that context, and vice-versa. Yet we could try to find a sentence r that followed from the former but not the latter. That would show that p was contributing more to the evaluation of the conditional than just a set of contexts where it is true.

Suppose p; is r true? (yes)
Suppose q; is r true? (no)

For this strategy, we could use p = "I exist", and q = "I am here."

If I am here, then I am not there. (True)
If I exist, then I am not there. (False)

My method was another common one: just take p to be "I am not here." Since this is true in no context, every conditional with p as an antecedent should sound the same: either all trivially true or all uninterpretable (or whatever, given our theory of conditionals). The point is that there shouldn't be possible to find an A and a B such that "if p, A" strikes us as true while "if p, B" strikes us as false.

Let's try to see exactly how Lewis makes the point. Is it just a bald appeal to intuition? He considers sentences like

"If someone is speaking here then I exist." (True)
"Forevermore, if someone is speaking here then I will exist." (False)

NB The argument works as an appeal to intuition, but only because we are actually assuming that "If someone is speaking here then I exist" is true, and this is only because we haven't taken the more restricted view of indexicals. Clearly, "If someone is speaking in the Dennes Room then Melissa exists" is not true; my existence does not depend on whether people continue to talk in the Dennes Room. However, other cases could be constructed, as above.


****
It has just occurred to me that this might in fact be possible, and the way of explaining e.g. Escher staircase experiences of the type that interest Susanna Siegel...
Siegel, Susanna (2004). Indiscriminability and the Phenomenal. Phil. Studies.