On Friday, July 5, 2002, at 01:16 PM, Tim May wrote: > The category and topos theory books I actually _own_ (bought through > Amazon) are: > >

Oops! I left out one of the most important and accessible of the books I have and recommend: * McLarty, Colin, "Elementary Categories, Elementary Toposes," 1992. An intermediate-level, moderate-length book. Covers a lot of interesting material. Here's what Baez says: "3) John Baez, Topos theory in a nutshell, http://math.ucr.edu/home/baez/topos.html and then try the books I recommended in "week68", along with this one: 4) Colin McLarty, Elementary Categories, Elementary Toposes, Oxford University Press, Oxford, 1992. which I only learned about later, when McLarty sent me a copy. I wish I'd known about it much sooner: it's very nice! It starts with a great tour of category theory, and then it covers a lot of topos theory, ending with a bit on various special topics like the "effective topos", which is a kind of mathematical universe where only effectively describable things exist - roughly speaking. " (end of Baez comments) By the way, the Web is a great resource for finding online books. Barr and Wells, who Bruno referred to, have put an updated version of their book "Toposes, Triples and Theories" online in PDF form. Search for it in the usual way. --Tim May (.sig for Everything list background) Corralitos, CA. Born in 1951. Retired from Intel in 1986. Current main interest: category and topos theory, math, quantum reality, cosmology. Background: physics, Intel, crypto, Cypherpunks