Readers of the cat list may be interested in the one meaningful post to Slate's "The Fray" in reply to Holt's MSRI "Diary" article. It was made by David Yetter: category theory David Yetter 28 Nov 2000 20:29 It is sad more than a decade on since the proof of the remarkable categorical coherence theorem of Shum that mathematicians can continue to view category theory as a mere linguistic convention or useless abstraction. Shum's theorem shows that axioms completely natural from the internal dynamic of category theory completely characterize framed tangles, relative versions of the framed knots and links which are central to smooth topology in 3 and 4 dimensions (notice the dimensionality of space and of space-time: hardly divorced from meaning.) Other categories satisfying the same axioms include the categories of representations of quantum groups, physically motivated algebraic structures which have become central objects of study for mathematicians from many old branches of mathematics. Indeed, Shum's theorem, a theorem of category theory, is the only really satisfying explanation for the intimate connection between quantum groups and low-dimensional topology.