Re: Some books on category and topos theory

From: Wei Dai <>
Date: Sun, 7 Jul 2002 00:23:31 -0700

Hi Tim, it's really interesting to see you here. (For those who don't
know, I knew Tim from the cypherpunks mailing list. Hal Finney was an
active member of the list as well. See if you're wondering
what a cypherpunk is.) Two of the most prominent cypherpunks I know are
now on my Everything mailing list. I wonder what that means... Anyway,

I remember your post on the cypherpunks list about category theory, but I
have to admit I didn't pay it much attention since it didn't seem very
relevent at the time. I guess this is my second chance to learn about
category theory, so there are some questions for you.

Suppose I had the time for only one book, which would you recommend? Also,
can you elaborate a bit more on the motivation behind category theory? Why
was it invented, and what problems does it solve? What's the relationship
between category theory and the idea that all possible universes exists?
Does it help understand or formalize the notion of "all possible
universes"? I know in logic there is the concept of a categorical theory
meaning all models of the theory are isomorphic. Does that have anything
to do with category theory?
Received on Sun Jul 07 2002 - 00:25:36 PDT

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