Return-Path: LOJBAN%CUVMB.BITNET@vms.dc.LSOFT.COM Received: from SEGATE.SUNET.SE (segate.sunet.se [192.36.125.6]) by xiron.pc.helsinki.fi (8.7.1/8.7.1) with ESMTP id UAA08399 for ; Fri, 5 Jan 1996 20:22:27 +0200 Message-Id: <199601051822.UAA08399@xiron.pc.helsinki.fi> Received: from listmail.sunet.se by SEGATE.SUNET.SE (LSMTP for OpenVMS v1.0a) with SMTP id 9C83963A ; Fri, 5 Jan 1996 19:22:26 +0100 Date: Fri, 5 Jan 1996 18:20:41 +0000 Reply-To: ucleaar Sender: Lojban list From: ucleaar Subject: Re: logical matters X-To: lojban@cuvmb.cc.columbia.edu To: Veijo Vilva Content-Length: 1346 Lines: 30 Date: Sat, 25 Nov 1995 18:25:57 -0800 From: "John E. Clifford" > And: > [I]t turns out that pc thinks A does entail E, while everyone else > (this includes a lot of people) thinks it doesn't. > pc: > Open challenge. Find me a logician (or even a mathematician who > knows a bit of logic) who thinks that AxFx does not entail ExFx in > the ordinary system (that is, one not doing free logic at the time he > says it. I am willing to concede defeat. > Now, it is true that in the jargon of mathematics and logic, "All Fs > are Gs" need not imply "Some Fs are Gs" [...]. But that is because > "everybody knows" (since 1858 at least) that "All Fs are Gs" is -- > in the jargon - - short for "for every x, if Fx then Gx" and the > conditional is material, true if the antecedent is false, as it > will be universally when ther are no Fs. Rather like Spanish, the > trick is not in the quantifier at all, but, in this case, in the > connective in the scope (BTW, anyone know a good Spanish logic book?). Okay. So {ro da broda} entails {da broda}. But all other uses of {ro} don't entail existence - {ro da poi kea broda cu brode} and {ro broda cu brode} entail neither {da broda} nor {da brode}. One ought to be encouraged, I think, to not use poi clauses with da, and to instead use logical connectives. coo, mie And