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From: lb0q@ANDREW.CMU.EDU (Leslie Burkholder)
Newsgroups: mod.ai
Subject: monotonicity
Message-ID: <MS.V3.10.lb0q.0.flemington.873.0@andrew.cmu.edu>
Date: Fri, 31-Oct-86 15:54:18 EST
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Posted: Fri Oct 31 15:54:18 1986
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The monotonicity property of validity: If an argument is deductively valid
then it cannot be made invalid by adding new premises. Equivalently: If X, Y
are finite sets of sentences and S a sentence, then if X entails S, then X
union Y entails S.

The monotonicity property of consistency: If a set of sentences is
inconsistent then it cannot be made consistent by adding to it a new
sentence. Equivalently: If X is a finite set of sentences, S some sentence,
and X is inconsistent, then so is X union {S}.

Leslie Burkholder