Thanks Tom.
It is exciting to see topos theory finding a place in the sun.
When I was participating in Dan Freed's TQFT seminars at
the University of Texas, we worked through one of Jacob's papers.
Despite the seemingly all-pervasive mistrust of category theory
(let alone topos theory), these semi
In the work I did at CMU on statistical causal reasoning, we made heavy use
of equivalence classes. Our algorithms would find equivalence classes of
causal models (generalizations of acyclic digraphs). If any edge occurred
in all elements of a class then it represented a cause between the
variabl
I first became aware of the equality issue from a Barry Mazur paper
http://www.math.harvard.edu/~mazur/preprints/when_is_one.pdf .
The Robert Goldblatt book "Topoi The Categorical Analysis of Logic" has
an honored place on my bookshelf but is mostly beyond me. I keep it
because it covers a lot
