28 May
2012
28 May
'12
6 a.m.
On Sat, 26 May 2012 19:48:26 -0400 (EDT), Michael Barr wrote:
Let me point out that not every structure comes with an obvious notion of morphism. --- [examples snipped] ---
The most common example: sets. The structure is based on membership. Virtually no one ever wants to restrict attention to functions that respect (preserve or reflect) membership (other than "preserve" between ordinals). Cheers, -- Fred [For admin and other information see: http://www.mta.ca/~cat-dist/ ]