[HN Gopher] Types versus sets (and what about categories?) (2022)
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Types versus sets (and what about categories?) (2022)
 
Author : matt_d
Score  : 15 points
Date   : 2023-08-31 21:39 UTC (1 hours ago)
 
web link (lawrencecpaulson.github.io)
w3m dump (lawrencecpaulson.github.io)
 
| dang wrote:
| Discussed at the time:
| 
|  _Types versus sets (and what about categories?)_ -
| https://news.ycombinator.com/item?id=30697421 - March 2022 (31
| comments)
 
| gylterud wrote:
| > various versions of Martin-Lof's intuitionistic type theory and
| finally the calculus of constructions of Coquand and Huet. In
| every case, they were created with no interpretation in mind.
| They were justified syntactically, for example via proofs of
| strong normalisation. Models came later.
| 
| Martin-Lof very explicitly discussed the denotational meaning of
| his theories. See for instance Section 5 of the SEoP entry on
| intuitionistic type theory.
| 
| https://plato.stanford.edu/entries/type-theory-intuitionisti...
| 
| TFA is correct that type theory is syntax, but it would be wrong
| to think of set theory as any less syntactic to the mind of an
| intuitionist. The semantics is the actual mathematical ideas
| going on within the head of the mathematician. Both type theory
| and set theory must be connected to these in order to be given
| meaning.
 
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