From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.science.mathematics.categories/3664 Path: news.gmane.org!not-for-mail From: Peter Freyd Newsgroups: gmane.science.mathematics.categories Subject: the term "pushout" Date: Tue, 06 Mar 2007 17:12:31 -0500 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 1241019443 9683 80.91.229.2 (29 Apr 2009 15:37:23 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 29 Apr 2009 15:37:23 +0000 (UTC) To: categories@mta.ca Original-X-From: rrosebru@mta.ca Tue Mar 6 21:39:56 2007 -0400 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Tue, 06 Mar 2007 21:39:56 -0400 Original-Received: from Majordom by mailserv.mta.ca with local (Exim 4.61) (envelope-from ) id 1HOky9-0001R5-Pv for categories-list@mta.ca; Tue, 06 Mar 2007 21:29:30 -0400 Original-Sender: cat-dist@mta.ca Precedence: bulk X-Keywords: X-UID: 18 Original-Lines: 22 Xref: news.gmane.org gmane.science.mathematics.categories:3664 Archived-At: Peter Johnstone asks who coined the term "pushout". On page 156 of Abelian Categories I wrote (43 years ago!): The word "pullback" and the ubiquity of the concept I learned from Lang, who also pointed out the pullback theorem and its importance. I plead guilty to "pushout"... (www.tac.mta.ca/tac/reprints/articles/3/tr3abs.html) MathSciNet lists Alex Heller's review of Abelian Categories as its second oldest use of the term "pullback" and its oldest use of "pushout". (Its first use of "pullback" is in Alex's review of John Gray's 1962 paper "Category-valued sheaves" -- no the stalks were not categoies.) It was my impression that Serge Lang invented the term "pullback" (his term for the dual notion was "co-pullback"). Note that I refrained from stating this impression. But I do claim to have invented the term "pushout" -- indeed, I've been know to cite this as my most visible contribution to mathematics.