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: In article <[EMAIL PROTECTED]>, : Jesse F. Hughes <[EMAIL PROTECTED]> wrote: : >Perhaps. I came into this thread secondhand. Why don't you tell us : >what you mean when you write, "all categories are in a sense : >imitations of the category of sets, the objects being imitations of : >sets and the morphisms being imitations of functions." It's very : >plausible that I don't know what the heck you mean. [EMAIL PROTECTED] writes: : Seems pretty clear to me. That's your problem. : The fact that set theory and category theory : can be used as foundations for mathematics is irrelevant to james dolan's : point, No, it isn't. Suppose you started out as a committed categorist, believing that using categories as a foundation was good and using sets was bad. Then, suppose a fellow categorist had reminded you, "all categories are in a sense imitations of the category of sets." That INVITES you to react, "Hmmm -- WHY is the category of SETS so SPECIAL -- WHAT is it ABOUT THAT category that makes it beat this relationship to ALL other categories? Why is it so central? Could it be -- gasp -- adequately FOUNDATIONAL??" : and is being dragged in uninvited. No, really, it isn't. The person alleging an unusually important central basic role for sets here IS JAMES DOLAN, not anybody else. : Suppose one had said instead, : "All homology and cohomology theories are in a sense imitations of : simplicial (co)homology." Presumably nobody is tempted to use simplicial : homology as a foundation for mathematics, and hence nobody is tempted : into failing to understand this statement. The analogy fails. I don't personally know WHETHER other homology and cohomology theories "imitate" simplicial cohomology. But the question of whether other categories "imitate" "the" category of sets is a lot more attackable, even on the basis of very limited general concerns like the ones I have been raising. : The fact that there are other ways of thinking about categories Other THAN WHAT?? Nobody ever suggested that any particular way was more or less relevant to the question of whether other categories "imitate" the category of sets! If the imitation is real then one would certainly expect it to remain equally real under ALL such ways!
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