From: Colin McLarty <colin.mclarty@case.edu>
To: "categories@mta.ca" <categories@mta.ca>
Subject: Functoriality of pullbacks of sets
Date: Sun, 18 May 2014 10:59:45 -0400 [thread overview]
Message-ID: <E1WmBDu-0000N2-GC@mlist.mta.ca> (raw)
It seems to me that Peter Freyd remarked it is easy to define pullbacks in
ZF (maybe with with global choice?) so that pullback along one side is
functorial, but hard to make it functorial on both sides. In other words
we can easily make base change functorial in the bases, but not easily make
it functorial in the bases at the same time as in the total spaces.
Can anyone direct me to a reference to that work?
thanks, Colin
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next reply other threads:[~2014-05-18 14:59 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-18 14:59 Colin McLarty [this message]
2014-05-19 14:03 ` pjf
2014-05-20 4:54 ` Vaughan Pratt
2014-05-22 1:24 ` Robin Cockett
2014-05-24 14:17 ` pjf
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