On Mon, Apr 2, 2012 at 6:30 PM, Marshall Lochbaum <mwlochb...@gmail.com> wrote: > A category is the collection of arrows AND objects. The objects alone do > not define the category, so there can be many categories with the same set > of objects.
That was my original impression. If this is the case, talking about "The category of sets" or "The category of rings" does not mean anything, since we do not know what arrows are in this category. > There is an additional requirement that there be an "identity" arrow from > each object to itself. This and composition make arrows act enough like > functions to be useful. Does this mean one arrow which is an identity for all objects? Or does this mean one arrow for each object which is an identity arrow? Or is it sufficient to have an arrow which is an identity arrow without regard for the cardinality of such arrows? Thanks, -- Raul ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
