Ideas from 'An Introduction to Modal Logic' by GE Hughes/M Cresswell [1968], by Theme Structure

[found in 'An Introduction to Modal Logic' by Hughes,G./Cresswell,M. [Methuen 1972,416-29470-7]].

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4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / b. Terminology of PL
A 'value-assignment' (V) is when to each variable in the set V assigns either the value 1 or the value 0
4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / d. Basic theorems of PL
The Law of Transposition says (P→Q) → (Q→P)
4. Formal Logic / B. Propositional Logic PL / 4. Soundness of PL
The rules preserve validity from the axioms, so no thesis negates any other thesis
5. Theory of Logic / K. Features of Logics / 4. Completeness
A system is 'weakly' complete if all wffs are derivable, and 'strongly' if theses are maximised