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consistent (Definition)

If $T$ is a theory of $\mathcal{L}$ then it is consistent iff there is some model $\mathcal{M}$ of $\mathcal{L}$ such that $\mathcal{M}\vDash T$ . If a theory is not consistent then it is inconsistent.

A slightly different definition is sometimes used, that $T$ is consistent iff $T\not\vdash\bot$ (that is, as long as it does not prove a contradiction). As long as the proof calculus used is sound and complete, these two definitions are equivalent.




"consistent" is owned by Henry.
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Also defines:  inconsistent
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Cross-references: definitions, complete, sound, Calculus, proof, contradiction, iff, theory
There are 64 references to this entry.

This is version 3 of consistent, born on 2002-08-28, modified 2002-09-04.
Object id is 3386, canonical name is Consistent2.
Accessed 14044 times total.

Classification:
AMS MSC03B99 (Mathematical logic and foundations :: General logic :: Miscellaneous)

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Consistent definitions? by Evandar on 2002-09-04 10:20:22
This definition actually disagrees with the definition in the First Order Logics entry, which defines a set of formulae to be consistent if they don't prove a contradiction.

This is one of the many examples of the lack of standardized terminology within logic. Maybe a note should be added to this entry to the effect that there is more than one definition.
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