"the theory of aesthetics put forward by a philosopher...is a test of the capacity of the system he puts forth to grasp the nature of experience itself. There is no test that so surely reveals the one-sidedness of a philosophy as its treatment of art and esthetic experience." John Dewey in "The Challenge to Philosophy" in Art as Experience.
There is no more overrated philosopher in the history of philosophy than Descartes. I would even venture that philosophy after Descartes has mainly been a history of attempts to recover from his mistakes. (I hardly ever say anything really negative about a philosopher and always look for the good in him or her. In Descartes, I look and look and find nothing.) Perhaps the best indicator of the misery of his thought is his anti-aesthetic tendency. Descartes is an anti-aesthetic thinker in a much deeper way than Plato, who, even though he outlawed imitative art from the ideal republic, at least called on others to defend such art, in particular Homer, whom he loved. Even Plato's Symposium, which gives us a theory of beauty, begins the ladder of love with the physical beauty of a boy. Descartes will have none of that. He goes out of his way not only to attack the senses as sources of knowledge but to attack the imagination. As a result he gives us many absurd theories which are, frankly, embarrassing to teach, as they often are in Introduction to Philosophy classes. Descartes' anti-aesthetic stance is important since I suspect that this is the basis of the overall neglect (and disparagement) of aesthetics and aesthetic experience within philosophy itself. If Descartes is the originator of modern philosophy he is also the originator of all that is mistaken in modern philosophy with regard to aesthetics. The only thing I admire in Descartes is his boldness and the relentless nature of his arguments. The thing that puzzles me the most is the way in which he was able to inspire later, and far greater, philosophers, such as Vico, Kant, Hegel, Nietzsche, Wittgenstein, Heidegger and Dewey. Of course, much of that inspiration was by way of reacting against him. Many philosophers have pointed out the deep problems with Cartesian dualism and with the representational theory of the mind. Few have looked at the way in which he attempted to erase anything aesthetic from human existence. You might say that he simply does not talk about aesthetics, although he did write his first book on music. But he does not talk about aesthetics for a reason, the reason being that sensuous and imaginative experience is of so little value to him.
Take as one example, his analysis of a piece of wax. He wants to argue that corporeal things, which the senses examine, are less distinctly known than the "I" which he had just argued is essentially a thinking being. He takes a piece of wax, more specifically a honeycomb, and observes that it has a "scent of flowers," a "honey flavor," a certain color, shape, is cold and hard, and gives a certain sound when hit. Then he erases, or at least changes, all of these phenomena by bringing it close to a fire. Since he believes that the same wax remains he concludes that what was "distinctly grasped" in the wax was none of these aspects. He then suggests that the wax never was any of the things mentioned, but "a body" that "manifested itself to me" in these ways, i.e. "something extended, flexible and mutable." Moreover, we do not even understand its nature as such through the imagination since the wax could be changed in ways I could not even imagine, or at least my imagination could not cover all of the possible ways it could be changed. And so I perceive the wax "with my mind alone."
But what do I perceive with my mind alone? Only the concept of infinitely extendable substance. Why this thing should be identical with the original piece of bees' wax is unclear to me. Descartes insists, paradoxically, that the piece of wax that is perceived by the mind "is the same piece of wax that I see, touch, and imagine" although he gives us no reason for believing this. Nor does he even give us a reason to believe that the infinitely extendable substance I "perceive" is really the piece of wax as the object of perception instead of simply an object of abstract thought. His conclusion that "perception of the wax is neither a seeing nor a touching, nor an imagining" is false on all three counts, since perception of the wax is all three. Moreover, it is not even clear what this mind is which, according to him, actually does perceive the wax. Presumably it is whatever does the calculation in determining the non-sensuous characteristics of the wax. (He completely ignores the fact that he has to manipulate the wax as sensuously perceived in order to get at these characteristics.)
Anyone who begins with "Now I shall close my eyes, I shall stop my ears, I shall disregard my senses, I shall even efface from my mind all of the images of corporeal things..." as Descartes begins his third meditation (Lafleur tr. pg. 91) eliminates the possibility of aesthetic experience (with the exception of the experience of beauty in mathematical formulae.)
Descartes, of course, used images and metaphors in his philosophical and scientific work. (See, Bellis, Delphine review of Claus Zittel, "Theatrum philosophicum. Descartes und die Rolle ästhetischer Formen in der Wissenschaft" in Early Science & Medicine 16, no. 3 (May 2011): 263-265.) of which his famous dreams and his evil demon are examples.
To be fair, he also had an influential philosophy of music which is described in this way in a recent article:
"Descartes's writings on music are representative of a large body of
contemporary theoretical works; they assume an essential relationship
between music and mathematics, and proceed to test the limits of that
relationship, basically functioning as large-scale mathematical proofs.
He first articulated his musical theory in the Compendium Musicae and
later developed it in his correspondence with Marin Mersenne. Both the letters and the Compendium, after establishing a mathematical
basis for music, posit a material link between music and the passions."
Vlock, Deborah M. "Sterne, Descartes, and the music in Tristram Shandy." Studies In English Literature (Rice) 38, no. 3 (Summer98 1998): 517-537. Apparently his approach to music was to reduce music to mathematics: not too surprising, given his general anti-aesthetic propensity (which as I mentioned above, only allows for mathematical beauty.)
A sympathetic account of Descartes' aesthetics of music can be found at "Descartes on Music: Between the Ancients and the Aestheticians" British Journal of Aesthetics (2012) 52 (4): 407-424.