From mboxrd@z Thu Jan 1 00:00:00 1970 X-Received: by 2002:a1c:8702:: with SMTP id j2-v6mr130669wmd.1.1527672813860; Wed, 30 May 2018 02:33:33 -0700 (PDT) X-BeenThere: homotopytypetheory@googlegroups.com Received: by 2002:adf:dd51:: with SMTP id u17-v6ls3452660wrm.12.gmail; Wed, 30 May 2018 02:33:33 -0700 (PDT) X-Received: by 2002:adf:b69f:: with SMTP id j31-v6mr163801wre.29.1527672813082; Wed, 30 May 2018 02:33:33 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1527672813; cv=none; d=google.com; s=arc-20160816; b=y2D0G1YjW6dvL28fc7QHxWnqtTtIpDo7tiWC0JVmoacpV08YjiAbo+jHNhlkCJPbzD HmB8pkZ8tPj9YyMYWiazp88jSfmUlgznA1G0FUvYw413HHPP+tDsIl9t1T7MwsiGhTyM kuFoKjAzEdDlf03uxDliqG0KmuVwnuvF2fxDS1A/QGuuw333hD84XTu7RzEJg5nJGyVL cf+o9kMQW35ajNc6u+VsnxNaB42IBX9HcyesoZcu1oCicaKXsYWJo78jblv+rc87Mtgy KaSX1k6nATaQHJYYFXfACmsdGxgZGXSDD//4AnyF7kNqjJvqv4ajAdZaBlLWmA0jiXuU dgvg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:arc-authentication-results; bh=ctvYox9NzK8ON4r6WkIDVBzVgveL8GmVDxP03AiLxv8=; b=mYK1IYTHzC+2N/O77/xvsDiksLxt4pRcMhbGEj2HAqrNpj8ZB0WeHXU5L/lbkvVTL5 9aI0QSRIPQCWuznvGxN04ZjC8ZW4OKyj3Bp0Tvq+bB31VjsScZGgn2pylME/IoFwDB5k op0BjEs0ULabfnqfqsyosr117I4/RL4EquDsF1cGs4FvLONRoJ1GtPofHAJB+aIribC6 v/bgvbSeBy73kK1pOIdvyHpj4bnWhcBqp5ET9vcn8j4Stq7CWJXwdp3JLrt5ef7ChSJU 1gDhu3RtdPml1yrRtFtyXIy33uexxnQn6Ngbw8aA/FkQsQx8wpFskoVD5TovF+WS7GYb GB5g== ARC-Authentication-Results: i=1; gmr-mx.google.com; spf=pass (google.com: best guess record for domain of stre...@mathematik.tu-darmstadt.de designates 130.83.156.239 as permitted sender) smtp.mailfrom=stre...@mathematik.tu-darmstadt.de Return-Path: Received: from lnx503.hrz.tu-darmstadt.de (mail-relay239.hrz.tu-darmstadt.de. [130.83.156.239]) by gmr-mx.google.com with ESMTPS id x3-v6si244638wrn.0.2018.05.30.02.33.32 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 30 May 2018 02:33:33 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of stre...@mathematik.tu-darmstadt.de designates 130.83.156.239 as permitted sender) client-ip=130.83.156.239; Authentication-Results: gmr-mx.google.com; spf=pass (google.com: best guess record for domain of stre...@mathematik.tu-darmstadt.de designates 130.83.156.239 as permitted sender) smtp.mailfrom=stre...@mathematik.tu-darmstadt.de Received: from fb04281.mathematik.tu-darmstadt.de (fb04281.mathematik.tu-darmstadt.de [130.83.2.21]) by lnx503.hrz.tu-darmstadt.de (8.14.4/8.14.4/HRZ/PMX) with ESMTP id w4U9Wton012149; Wed, 30 May 2018 11:32:55 +0200 (envelope-from stre...@mathematik.tu-darmstadt.de) Received: from fb04209.mathematik.tu-darmstadt.de (fb04209.mathematik.tu-darmstadt.de [130.83.2.209]) by fb04281.mathematik.tu-darmstadt.de (8.12.3/8.12.3/Debian-7.2) with ESMTP id w4U9XVi6003182; Wed, 30 May 2018 11:33:31 +0200 Received: by fb04209.mathematik.tu-darmstadt.de (Postfix, from userid 11003) id 537151A0C44; Wed, 30 May 2018 11:33:31 +0200 (CEST) Date: Wed, 30 May 2018 11:33:31 +0200 From: Thomas Streicher To: Michael Shulman Cc: Thorsten Altenkirch , "homotopyt...@googlegroups.com" Subject: Re: [HoTT] Re: Where is the problem with initiality? Message-ID: <20180530093331.GA28365@mathematik.tu-darmstadt.de> References: <06B9C5AB-C7CB-4CB5-B951-64E0C4180AD9@exmail.nottingham.ac.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) X-PMX-TU: seen v1.2 by 5.6.1.2065439, Antispam-Engine: 2.7.2.376379, Antispam-Data: 2018.5.30.92416 X-PMX-RELAY: outgoing In my eyes the so called initiality problem is not a problem of semantics of type theory. Models of type theory are essentailly algebraic objects and thus as observed by Vladimir do admit an initial one. Syntax based on categorical combinatorsis fine in principle and useful for implementaion. That categorical syntax and ordinary syntax are isomorphic is just a purely syntactic result allowing one to replace correct algebraic syntax by one more accessible for the human mind. But it is important to show that this replacement is faithful w.r.t. the mathematically correct one. Thomas