From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 1 Jun 2018 14:27:24 -0700 (PDT) From: Matt Oliveri To: Homotopy Type Theory Message-Id: <864df164-59e9-4609-8e81-7c334be11e98@googlegroups.com> In-Reply-To: References: <06B9C5AB-C7CB-4CB5-B951-64E0C4180AD9@exmail.nottingham.ac.uk> <20180530093331.GA28365@mathematik.tu-darmstadt.de> <5559377C-94C9-422E-BBF7-A07AFA4B7D04@exmail.nottingham.ac.uk> <3D1D292E-1EFF-4EA2-8233-B55FDA5CE8A5@gmail.com> <5A8268CE-26C1-4FD5-A82F-8063C08EF115@exmail.nottingham.ac.uk> <37CBB960-C4F1-4B97-92E6-28462A0591C1@gmail.com> <2b190a31-7985-4e6b-9f69-ed244ea64d7d@googlegroups.com> Subject: Re: [HoTT] Re: Where is the problem with initiality? MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_10891_96265151.1527888444236" ------=_Part_10891_96265151.1527888444236 Content-Type: multipart/alternative; boundary="----=_Part_10892_2084848911.1527888444236" ------=_Part_10892_2084848911.1527888444236 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On Friday, June 1, 2018 at 1:45:42 PM UTC-4, Eric Finster wrote: > > So from an internal perspective, I cannot think of any reason to > insist on decidability. > I agree with this. And in particular, I think QIITs can define intrinsic syntax of (fully-annotated) extensional type theroy just fine. Equality reflection would be an extra equality constructor. Isn't that right? What do Thorsten and team think of that? Is it an infelicity of QIITs, perhaps because they're hSet truncated? Or is there a problem with ETT that structuralism doesn't shed light on? Or is ETT maybe not so bad? ------=_Part_10892_2084848911.1527888444236 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: 7bit
On Friday, June 1, 2018 at 1:45:42 PM UTC-4, Eric Finster wrote:
So from an internal perspective, I cannot think of any reason to
insist on decidability.

I agree with this. And in particular, I think QIITs can define intrinsic syntax of (fully-annotated) extensional type theroy just fine. Equality reflection would be an extra equality constructor. Isn't that right? What do Thorsten and team think of that? Is it an infelicity of QIITs, perhaps because they're hSet truncated? Or is there a problem with ETT that structuralism doesn't shed light on? Or is ETT maybe not so bad?
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