From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.science.mathematics.categories/7055 Path: news.gmane.org!not-for-mail From: Michael Barr Newsgroups: gmane.science.mathematics.categories Subject: Re: Lawvere and Leibniz Date: Mon, 14 Nov 2011 10:00:24 -0500 (EST) Message-ID: References: Reply-To: Michael Barr NNTP-Posting-Host: lo.gmane.org Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-Trace: dough.gmane.org 1321360335 23616 80.91.229.12 (15 Nov 2011 12:32:15 GMT) X-Complaints-To: usenet@dough.gmane.org NNTP-Posting-Date: Tue, 15 Nov 2011 12:32:15 +0000 (UTC) Cc: "categories@mta.ca list" To: David Roberts Original-X-From: majordomo@mlist.mta.ca Tue Nov 15 13:32:10 2011 Return-path: Envelope-to: gsmc-categories@m.gmane.org Original-Received: from smtpx.mta.ca ([138.73.1.4]) by lo.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1RQIBL-0000uE-Mz for gsmc-categories@m.gmane.org; Tue, 15 Nov 2011 13:32:07 +0100 Original-Received: from mlist.mta.ca ([138.73.1.63]:33737) by smtpx.mta.ca with esmtp (Exim 4.76) (envelope-from ) id 1RQIA9-0001bQ-VK; Tue, 15 Nov 2011 08:30:53 -0400 Original-Received: from majordomo by mlist.mta.ca with local (Exim 4.71) (envelope-from ) id 1RQIA8-0005NW-Dr for categories-list@mlist.mta.ca; Tue, 15 Nov 2011 08:30:52 -0400 In-Reply-To: Precedence: bulk Xref: news.gmane.org gmane.science.mathematics.categories:7055 Archived-At: Very interesting. Curiously, nowhere in the post is its author identified. Some of the comments refer to a Dennis, but that is no one I can identify. Russell's view strikes me as especially inane. Had Weirstrass not produced his concept of limit, would Russell have simply discarded calculus as nonsense? An awful lot of problems were solved correctly, even before Weierstrass--would Russell have discarded them. Another point that bothered me was the tossing aside, without explanation, of dx^2 because it was infinitesimal vis-a-vis dx. Better to do what Robinson did, divide by dx and then take the ordinary part as the answer. Perhaps he could have introduced a different "equality" symbol. Still, it was a nice mention of categories. Michael [For admin and other information see: http://www.mta.ca/~cat-dist/ ]