From pycyn@aol.com Wed May 24 10:35:12 2000 Return-Path: Received: (qmail 21457 invoked from network); 24 May 2000 17:35:12 -0000 Received: from unknown (10.1.10.26) by m4.onelist.org with QMQP; 24 May 2000 17:35:12 -0000 Received: from unknown (HELO imo-d05.mx.aol.com) (205.188.157.37) by mta1 with SMTP; 24 May 2000 17:35:12 -0000 Received: from Pycyn@aol.com by imo-d05.mx.aol.com (mail_out_v27.9.) id a.7f.4c32ae2 (618) for ; Wed, 24 May 2000 13:35:09 -0400 (EDT) Message-ID: <7f.4c32ae2.265d6ccd@aol.com> Date: Wed, 24 May 2000 13:35:09 EDT Subject: Logic and Law To: lojban@egroups.com MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: AOL 3.0 16-bit for Windows sub 41 From: pycyn@aol.com X-Yahoo-Message-Num: 2831 Reading a thread on the international use of Lojban, specifically as a language for patents and so a part of the legal apparatus, reminded me of one important fact about legal reasoning. Quite aside from the use of inventive equivocation and ad hoc reinterpretation which play major roles both in drafting legal documents and in presenting cases in court, there is the fact that the logic of the law is not classical first order (or higher) predicate logic, but rather some kind of local relevance logic. The classic example of this comes from the MULL project of a couple of decades ago. In classical logic, an inconsistent set of premises validly entails absolutely any sentence at all. The MULL project demonstrated that the US Tax Code was in fact inconsistent. BUT it also found that there were conclusions (court verdicts, indeed) that could not be derived from that Code, even though they could be made to follow from it. The failure was typically the result of the demonstration taking into account parts of the code that were not judged to be germane to the issue at hand -- even though a logically tight (classical) connection could be made. Many of the unaccepted demonstrations did not even take advantage of the inconsistency of teh Code. So, on the one hand, having the law in a logical format (one of the achievements of MULL), allows us to see these facts and also allows us to begin to work out the rules that underlie the relevant sense of relevance, but, on the other hand, they do not allow us simply to use the apparatus to draw conclusions.