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From: olcott <polcott333@gmail.com>
Newsgroups: sci.logic
Subject: The key undecidable instance that I know about
Date: Sun, 9 Mar 2025 12:15:13 -0500
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Is the Liar Paradox True or False?

LP := ~True(LP)

?- LP = not(true(LP)).
LP = not(true(LP)).

?- unify_with_occurs_check(LP, not(true(LP))).
false.

Its infinitely recursive structure makes it neither true nor false.

-- 
Copyright 2025 Olcott "Talent hits a target no one else can hit; Genius
hits a target no one else can see." Arthur Schopenhauer