more from GE Hughes/M Cresswell

### Single Idea 9544

#### [catalogued under 5. Theory of Logic / K. Features of Logics / 4. Completeness]

Full Idea

To say that an axiom system is 'weakly complete' is to say that every valid wff of the system is derivable as a thesis. ..The system is 'strongly complete' if it cannot have any more theses than it has without falling into inconsistency.

Gist of Idea

A system is 'weakly' complete if all wffs are derivable, and 'strongly' if theses are maximised

Source

GE Hughes/M Cresswell (An Introduction to Modal Logic [1968], Ch.1)

Book Reference

Hughes,G./Cresswell,M.: 'An Introduction to Modal Logic' [Methuen 1972], p.19

A Reaction

[They go on to say that Propositional Logic is strongly complete, but Modal Logic is not]