Say WHAT? Nobody is saying Descarte's. Descarte's is NEVER, EVER
right, possessive or no possessive, although I do occasionally write
(and backspace over) "Chalmer's".
We're debating Descartes' vs. Descartes's, for the possessive of course,
and I happen to have a reknowned grammar book ("The Elements of Style")
in front of me, and I also happen to be right (unless the style has
changed since whenever the book was published, which is a possibility).
--
sentience@pobox.com Eliezer S. Yudkowsky
http://tezcat.com/~eliezer/singularity.html
http://tezcat.com/~eliezer/algernon.html
Disclaimer: Unless otherwise specified, I'm not telling you
everything I think I know.