From newshub.ccs.yorku.ca!ists!helios.physics.utoronto.ca!news-server.csri.toronto.edu!rutgers!jvnc.net!netnews.upenn.edu!sagi.wistar.upenn.edu Mon May 25 14:07:09 EDT 1992
Article 5843 of comp.ai.philosophy:
Path: newshub.ccs.yorku.ca!ists!helios.physics.utoronto.ca!news-server.csri.toronto.edu!rutgers!jvnc.net!netnews.upenn.edu!sagi.wistar.upenn.edu
>From: weemba@sagi.wistar.upenn.edu (Matthew P Wiener)
Newsgroups: comp.ai.philosophy
Subject: Self-referential logic
Message-ID: <78706@netnews.upenn.edu>
Date: 22 May 92 14:12:28 GMT
References: <1992May22.030205.21479@news.media.mit.edu>
Sender: news@netnews.upenn.edu
Reply-To: weemba@sagi.wistar.upenn.edu (Matthew P Wiener)
Organization: The Wistar Institute of Anatomy and Biology
Lines: 16
Nntp-Posting-Host: sagi.wistar.upenn.edu
In-reply-to: minsky@media.mit.edu (Marvin Minsky)

In article <1992May22.030205.21479@news.media.mit.edu>, minsky@media (Marvin Minsky) writes:
>The point is that it appear to be impractical to make anything the
>resembles common-sense self-reference without accepting inconsistency.
>It is a practical matter indeed.  Logicians have tried ways to evade
>this, e.g., stratifications, etc. -- but the result has always been
>too ponderous to be useful.

Actually, there now seems to be a useful approach to self-reference.
Barwise and Etchemendy have developed a logic based on Aczel's non-
well-founded version of set theory, and it provides an intuitively
appealing approach to the Liar Paradox and its numerous variants.
See their THE LIAR for details.  In short, they attach meaning and
truth not just to sentences, but sentences embedded in a situation.
And the situations can include sentences and their truth-values.
-- 
-Matthew P Wiener (weemba@sagi.wistar.upenn.edu)


