Well, you might want to look at this: \item (With. M.-A. Knus), Extensions of Derivations. Proc. Amer. Math. Soc. {\bf 28} (1971), 313--314. This is more homological algebra than category theory. The story is that someone had done this in a special case (where the center was local I think) in a dozen pages and someone else had extended it to semilocal and Knus was lecturing at the ETH on his extension to arbitrary centers (but the ambient ring was always semi-simple = Hochschild dimension 0). As Knus was lecturing I said to myself that there had to be a better way. And there was. It took only a paragraph and use only Hochschild dimension 1 besides. The rest of the two pages was intro and bibliography. Although it isn't category theory it exemplifies the categorical way of thinking, dealing with generic properties and the like. Incidentally, the paper was originally rejected. The referee's report said, "The only possible reason for publishing this is that it has been so badly handled in the literature"! I would have thought that an excellent reason to publish it. Only the fact that the editor was a personal friend who said he would publish it if I insisted, allowed it to see the light of day. But I have long thought it a "proof from the book". Michael On Wed, 24 Jun 2009, Ellis D. Cooper wrote:
Dedicated to the memory of Paul Erdos, Martin Aigner and Gunter M. Ziegler's book (with the Subject title) offers examples of proofs with "brilliant ideas, clever insights and wonderful observations." They include chapters on Number Theory, Geometry, Analysis, Combinatorics, and Graph Theory. My question is, what would likely be included if there were a chapter on Category Theory?
Ellis D. Cooper
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