On Wed, 11 Jul 2007, Fred Linton wrote:

Michael asked:

...

I have seen a reference to Isbell duality. Can anyone point me to a definition and any results?

Perhaps John's 196x-ish "Structure of Categories" paper is what you seek.

-- F.

I think it's more likely to refer to John's unpublished (indeed, unwritten) paper "Some concrete dualities". This appeared as an abstract in the AMS Notices in 1974 (vol. 21, pp. A567-8), and I heard John talk about it at an Oberwolfach meeting in 1975. In 1981 I asked John when we could expect to see the paper in print (since I was then writing "Stone Spaces", in which I wanted to refer to it), and he replied that he was still working on the write-up of his 1973 Oberwolfach talk. (The implication was that he'd get around to the 1975 talk when the earlier one was out of the way, but I'm pretty sure he never did.) Peter