Thursday, July 13, 2006

Demonstratives and Apriority

Can non-trivial thoughts involving demonstratives ('this' or 'that') be a priori? (By "non-trivial", I mean that the truth of the thought depends on what is being demonstrated; not just any old target will do.) Chalmers' epistemic space framework suggests not, since it treats what's demonstrated as variable across centred worlds. That means that there will be some epistemically possible scenarios in which the target of my demonstration will be "any old thing", and hence my thought will come out false at that scenario, and hence it actually fails to be a priori.

But we might've expected the contrary result to be possible. Consider the following passage taken out of context from Laurence Bonjour's In Defense of Pure Reason (pp.57-58):
I am presently looking at two books on my desk. Both are darkish blue, but not quite the same shade of darkish blue, though my rather meagre color vocabulary contains no names for these specific shades nor any other way of indicating them linguistically. On this basis, I come to believe and, so far as I can see, to know a priori a certain proposition that I can only indicate indirectly but cannot adequately express in language, the proposition that nothing could be both of these colors all over at the same time...

(Bonjour uses this to show that a priori justification cannot be accounted for merely by "linguistic convention". My current purposes are completely different.)

Now, one way that I would be tempted to state the described a priori thought is as follows:

(D) Nothing could be that colour [mental nod towards first book] and that colour [mental nod towards second book] all over at the same time.

Is D a priori? It seems to depend on whether the demonstrated colours are themselves part of the tokened thought, or whether the demonstrations are mere placeholders. If the colours are "built in", then the resulting thought is certainly a priori. (Those two colours are themselves incompatible in all scenarios.) However, if the thought instead contains "placeholders", then it is not a priori, since this allows different targets to "fill the gap" in different scenarios. In particular, it allows a scenario in which we pick out the same colour twice. Such a scenario falsifies D, so understood, since things can of course be one and the same colour all over at the same time. Failing to be true at all scenarios, D thereby fails to be a priori.

As I understand it, Chalmers' framework requires that we adopt the second interpretation: demonstratives are variable placeholders, and so "non-trivial" demonstrative thoughts cannot be a priori. Is that a problem? Should we want to allow the first interpretation? We will at least want to allow some thought or other to have this "built in" content. But perhaps we should deny that those are "demonstrative thoughts" any longer. We might instead suggest that Bonjour was thinking something along the lines of:

(D*) "Nothing could be colour1 and colour2 all over at the same time." (Those "colour" labels might be replaced by appropriate items of direct phenomenology, say mental images of the colours in question. We want epistemically rigid designation, anyway, however that is done. The two colours should be held fixed across all scenarios.)

Note that there's nothing essentially "demonstrative" about D*. Lacking the vocabulary to express the thought directly, perhaps the best we could do verbally is to say something like D instead, and point to the two colours we have in mind. But really it is the two colours, and not the pointing, that we do in fact have in mind. So I think that provides some independent support for the claim that, contrary to my initial speculation, Bonjour's a priori thought is not a demonstrative one.

Is that the best way to make sense of this problem? (Is the answer to that question -- or this one -- a priori? Heh.)


  1. I think that (D*) formulation of it makes more sense. If we take the thought as intentional act, the intentional content in the thought are the both colors of the books which are in front of Bonjour. So by color1 and color2 we would mean these specific intentional contents.

    On the side note, I wonder though if D* in that exact form is a priori. Chimerical colors of P.Churchland show that things like "color which is as dark as the darkest black and at same time blue" can be experienced. Now maybe chimerical color which is in same moment color1 and color2 of the books might not be experienced. But to be sure of that, should we look into neuroscience and do experiments? If so, the claim might not as well be a priori.
    The claim might be changed somewhat, something like "Nothing could be in same time the color1 and not the color2, and color2 but not the color1", but then it is trivially a priori.
    I wonder about "color1 and color2 are different". Maybe that could count as non-trivial a priori (though of course not involving demonstratives)?

  2. Hi Richard,

    Actually, I think thoughts involving demonstratives can be a priori. E.g. *That object is there (if it exists)* can be a priori, as can *That object looks this way to me*. It's only experiential demonstratives that are primitive on my framework. Other demonstratives are linked to those, and there can be a priori connections among them.

    In any case, I agree with your diagnosis of the color case. I think the a priori color thoughts in the vicinity of the color-thoughts you're discussing don't really involve demonstrative phenomenal concepts, but a sort of qualitative concept of the color in question. There's more on the distinction between the different sorts of thought in the vicinity in my paper on The Content and Epistemology of Phenomenal Belief.

  3. Ah, thanks for the pointer. Do you think there can be a priori demonstrative thoughts whose truth depends on what is actually ostended (and hence qualifies as "non-trivial" in my sense)? At least, the example of *That object is there (if it exists)* doesn't seem to have any such constraint. (It would be true no matter what we were pointing at, right?)

  4. Hi, right, I don't think the apriority of a demonstrative thought can depend on what one is pointing at. And yes, the relevant sort of tokens of *That object is there (if it exists)* will be true no matter what one is pointing at.

  5. I think the only 'apriori' thing about this is to say 'this sensation is different from that sensation'. And only the person having the sensation will know the truth of that. But they will surely 'know' it in the 'a priori' sense.

    To talk about the actual colours of the book loses all a prior status. Saying 'nothing could be this colour and that colour at the same time' is a fact about the world which would surely remain to be seen, and could never be 'proved'. But to say 'nothing could *appear* to be this colour and that colour at the same time' is quite possiby perfectly true for any individual. And only they could know.

    djc, it must be fun to have 'phenomenal belief'. I'm sure the meaning is highly specific, but it really does sound quite funny.


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