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Article #84

Equivalence of Strong completeness and categoricity

#84
From: Jean-Marc Alliot
Date: Wed, 22 Jul 1992 20:58
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This question is perhaps trivial but...

I am first going to give the definition I am using, since many people
use the same words for different things: 

Consistency: A system is consistent if, for any wff F, we
can not have at the same time (F is a theorem) and (not F is a
theorem). 

Categoricity: a system is categoric if, for any wff F, we have either
(F is theorem) or (not F is a theorem).

Strong completeness: a system based on a set S of axioms is strongly
complete if for any wff F, we have either (F is a theorem) or (F added
to S is an inconsistent system).


Now the questions:

1) It seems quite clear that in any system which is a superset of
propositional calculus Categoricity and Strong completeness are
equivalent. However a short and clear demonstration would be very much
welcome.

2) Does the property hold in the general case (I especially think of
intuitionist logic) ?

If the question is too trivial, a reference to a book giving the
answers would be also welcome.
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Message-ID: <1992Jul22.205827.16651@cenatls.cena.dgac.fr>
Path: arc1-ca.pugleaf.net!sparky!uunet!mcsun!corton!cenaath.cena.dgac.fr!geant!alliot

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Path: arc1-ca.pugleaf.net!sparky!uunet!mcsun!corton!cenaath.cena.dgac.fr!geant!alliot
From: alliot@cenatls.cena.dgac.fr (Jean-Marc Alliot)
Newsgroups: sci.logic
Subject: Equivalence of Strong completeness and categoricity
Message-ID: <1992Jul22.205827.16651@cenatls.cena.dgac.fr>
Date: 22 Jul 92 20:58:27 GMT
Sender: news@cenatls.cena.dgac.fr
Organization: Centre d'Etudes de la Navigation Aerienne, Toulouse, France
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