Oh, I should tell you that I finally finished Janet Broughton's Decartes' Method of Doubt and must say that it only confirmed for me Gilson's critique of the Cartesian Project. Obviously I can't go into any detail on a Facebook Wall but can for now say this much: Broughton pretty much depicts the Cartesian Project as a knowledge algorithm from beginning to end, and Gilson would say that this is a permutation of the error of logicism, and I daresay Gilson is right. Metaphysics in order to get anywhere must start with being and not with epistemological procedure. Broughton admits, despite her tremendous sympathy with the Cartesian Project, that Decartes' doubt, if it is made to work at all, replaces the real world of color and dynamism with a very pale one of mechanical geometric extension, and that, again, only if it works. The Cartesian Project remains unrehabilated. But thanks for the recommendation.
"Metaphysics in order to get anywhere must start with being and not with epistemological procedure." But how can we trust our metaphysics to go anywhere if we do not know what we can know and how?
Yeah, that is, of course, an enormity of a conundrum. But the very possibility of an epistemology at all must pre-suppose an ontology. Descartes gets the Cogito or, as Broughton suggests, the Dubito not because it is, as Broughton argues, a function of his epistemological algorithm but because he finally uncovers at least one of his assumptions, and that is his own being. One cannot simply make up the hermeneutic circle from scratch.
"Descartes gets the Cogito... because he finally uncovers at least one of his assumptions, and that is his own being." I suppose it is possible to believe that his recognition that "Cogito" is indubitable is also a recognition that "Sum" and "Sum res cogitans" are indubitable. But I also suppose that it is possible to believe that the indubitability of "Sum" and "Sum res cogitans" *follows from* the indubitability of "Cogito." And I don't see how the latter can be inferred from the former. Of course, I am keeping things in the epistemological mode, stressing claims *about indubitability*. Do you question the inference of "p" from "'p' is indubitable?"
If one starts from the "Cogito" alone, it is quite frankly hard to see how the "sum" follows if by "sum" you mean a singular identity. The "sum" follows the "Cogito" only on the assumption that grammar corresponds to what is real, and I don't see why when we are to doubt basic arithmetic, we should not doubt grammar's adequation to reality as well. Yes, grammatically the "sum" follows the "cogito" insofar as both are first person singular verbs, but does that mean where there is sensation of thought, there is also an identifiable "ego", "I", "self"? Whatever this thing called thinking is may just as well point to a bunch of "selves" or even, as Nietzsche points out, to an "it". Furthermore, to get to some kind of an identity requires an additional assumption of Paramedian eternity.
Well, whether "sum" follows from "cogito" depends a lot on what is affirmed by "cogito." And recall that the question is not just whether "sum" follows but whether the indubitability of "sum" follows from the indubitability of "cogito." So Descartes not only needs to affirm a lot with "cogito," he needs to affirm it all *as indubitable*. Dubious, I agree.
So, if Cogito, ergo sum is dubious, what's left of the Cartesian Project?
Oh, well, there are some lovely party favors.