Descartes on colors and shapes

As is well known, Descartes argues that the sensation of white in our minds when we look at snow does not resemble whatever it is in the snow that produces this sensation in us. (He puts this point in different ways in different places; e.g., sometimes he says that our sensory awareness of whiteness leaves us "wholly ignorant" of what the snow is like (Principles of Philosophy, I.68).) The same holds for many other sensory qualities: the pain we feel when we put our finger in the fire does not resemble anything in the fire, the sweet scent we have of honey does not resemble anything in honey, and so on.

But what about my sensory awareness of the shape of a snowball, a fireplace, or a honey jar? In these cases, Descartes takes a different line: "We know size, shape, and so forth in quite a different way from the way in which we know colors, pains and the like" (PP, I.69). What is this difference? Descartes writes: "there are many features, such as size, shape, and number which we clearly perceive to be actually or at least possibly present in the in objects in a way exactly corresponding to our sensory perception or understanding" (PP, I.70).

So the obvious question here is: what makes our sensory perception of shape different from our sensory perception of color, so that the former but not the latter can 'correspond to' or resemble the thing represented? Descartes' argument in the final quotation above strikes me as weak. Descartes says that we clearly perceive that our sensory perceptions of shapes either (i) actually resemble or (ii) possibly resemble something in the objects themselves. Regarding (i), I strongly doubt that we can clearly and distinctly perceive anything about the relationship between the ideas in our minds and the objects outside of us -- we would need to be able to 'step outside of our minds,' as it were, to survey and compare both the contents of our minds and objects as they really are. And if we take (ii), then it at least seems possible to me that my sensory awareness of white resembles some property in the object itself. Of course, that would be a fortunate coincidence, but coincidences are not impossible. (Perhaps Descartes' notion of possibility rules out more than our modern one(s)?)

So, is there a way to save Descartes' position that our sensory perceptions of shapes can/do resemble something in the objects themselves, whereas our sensor perceptions of colors can/ do not? Perhaps the piece of wax section in Meditation 2 could be of some help here?

Update: I had forgotten that this very problem also arises, perhaps more expiciltly, in Locke's Essay: Locke says that our ideas of primary qualities (shape, mobility, solidity, extension, and number) really do "resemble" their causes in the objects that we perceive (II.viii.15). And perhaps because this claim is more front-and-center in Locke than Descartes, commentators on the Essay from Berkeley through today have had difficulty making good sense of this claim. Berkeley brings out the problem clearly: is the idea square in my mind actually square-shaped? Is my idea of motion itself moving?


Greg Frost-Arnold said...

Ian: I'd like to know explicitly why (as you say) "it is reasonable to suppose" that mental/ internal shapes somehow resemble something in the distal objects, if we assume (with Descartes) that it is UNreasonable to suppose that mental/ internal colors resemble something in external objects. My gut feeling/ intuition is that there IS something very reasonable aobut Descartes' claim -- I just want to get explicit about what that is.

Kenny: This suggestion (which sounds like Moritz Schlick's epistemological "point-coincidence" argument) is appealling -- I can't find anything like it in Descartes, but I don't have the 10 volumes of Adam and Tannery committed to memory, so it could be there. I'm really out of my depth here, but here's my knee-jerk reaction.
(1) It seems like some sensory qualities "are available to" multiple sensory modalities: I both hear and feel loud music (tones and vibrations).
(2) Is it really the case that the 'shape' of a baseball made available through our visual system is one and the same thing as the 'shape' made available via our tactile system?

Finally, I just wanted to mention that Kant pretty clearly does not follow Descartes (and the other mechanical philosophers) on this point -- I wonder whether something like the line of thought in the original post had something to do with his position.

Greg Frost-Arnold said...

Hi Frank--

Unfortunately, the documents (RCC 090-16 and 102-63) are not currently publicly available. If you can read German, you can request them from the Archives of Scientific Philosophy in the University of Pittsburgh library system. Also (here comes a shameless self-promotional plug), my translation of and commentary on those notes are being published as a book from Open Court Press, hopefully appearing in early 2007. Also, highlights from the notes will appear in an article by Paolo Mancosu that should appear in History and Philosophy of Logic pretty soon.

Greg Frost-Arnold said...

Another update: we don't need to go all the way to Kant to find the worry that I raised in the original post about Descartes' view. I think Leibniz has it already in section 12 of his Discourse on Metaphysics.

"It is even possible to demonstrate that the notions of size, shape, and motion are not as distinct as is imagined, and that they contain something imaginary and relative to our perception, as do (though to a greater extent) color, heat, and other similar qualities, qualities about which one can doubt whether they are truly found in the nature of things outside ourselves."

Leibniz does draw a distinction between shape and size on the one hand, and other sensory qualities on the other -- but for Leibniz, unlike Descartes, this is a difference of degree, not of kind.