On Sun, May 10, 2015 at 05:01:59PM +0200, Bruno Marchal wrote: > > On 09 May 2015, at 02:56, Russell Standish wrote: > > >On Fri, May 08, 2015 at 08:47:22AM +0200, Bruno Marchal wrote: > >> > >> > >>All argument in math are from incredulity. > > > >Not at all. They should be precise deductions from a given set of > >premisses, using agreed rules of logic. > > I was alluding to the fact that for proving negation of A, we prove > A -> f, and we take for granted that f is incredible (except before > breakfast perhaps :) >
In a technical sense, perhaps, but we can simply say "proof by contradiction" is identical with the proof of f, and is a perfectly acceptable mathematical technique. Even axiomatic in the rules of logic, I would say. On the other hand, proof by incredulity is no proof. For example it is pretty incredible for a teapot to be orbiting Jupiter. But does that prove no such teapot exists? That is the sort of proof by incredulity we're talking about, and the sort of proof the MGA is. -- ---------------------------------------------------------------------------- Prof Russell Standish Phone 0425 253119 (mobile) Principal, High Performance Coders Visiting Professor of Mathematics hpco...@hpcoders.com.au University of New South Wales http://www.hpcoders.com.au ---------------------------------------------------------------------------- -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
