I don't think one should blame the guy whose remarks Peter quoted. He is not a mathematician and presumably knows nothing more than some college level mathematics. He has picked up that attitude from the high-powered mathematicians that inhabit places like MSRI (and the CRM, Fields Inst., and PIMS in Canada). Ignoring the fact that category theory was fathered by two of the most eminent mathematicians of the last century and god-fathered by arguably the very greatest, they still go around saying that it is without content and nothing but meaningless abstraction. I was unaware of what David Yetter mentioned, but I am certainly aware of the crucial role categories had in proving the Weil conjectures and the fact that people like John Baez seem to believe that higher dimensional categories will be important in physics. I might also point out that categories were the right framework for Kaplansky's very elegant proof of the Auslander-Buchsbaum theorem. And here is a question: are categories more abstract or less abstract than sets? Michael