From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.science.mathematics.categories/4333 Path: news.gmane.org!not-for-mail From: Thomas Streicher Newsgroups: gmane.science.mathematics.categories Subject: question to Colin about uniqueness in his Replacement axiom Date: Tue, 18 Mar 2008 12:50:50 +0100 (CET) Message-ID: NNTP-Posting-Host: main.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Trace: ger.gmane.org 1241019877 12797 80.91.229.2 (29 Apr 2009 15:44:37 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 29 Apr 2009 15:44:37 +0000 (UTC) To: categories@mta.ca Original-X-From: rrosebru@mta.ca Tue Mar 18 19:03:06 2008 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Tue, 18 Mar 2008 19:03:06 -0300 Original-Received: from Majordom by mailserv.mta.ca with local (Exim 4.61) (envelope-from ) id 1JbjkP-00079l-1R for categories-list@mta.ca; Tue, 18 Mar 2008 18:53:29 -0300 Original-Sender: cat-dist@mta.ca Precedence: bulk X-Keywords: X-UID: 97 Original-Lines: 11 Xref: news.gmane.org gmane.science.mathematics.categories:4333 Archived-At: Mike Shulman pointed me out a faulty formulation in my lengthy mail from last Saturday; I take the opportunity of formulating it correctly: In your Replacement axiom (p.48 of your "Philosophia" article) you psotulta the existence of a map f : S -> A such that S_x \cong x^*f for all x : 1->X. Can you prove that this f is unique up to isomorphism, i.e. that wellpointedness for maps entails wellpointedness for families? Thomas