Combining Texts

All the ideas for 'Symbolic Reasoning', 'A Note on the entscheidungsproblem' and 'An Introduction to Modal Logic'

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6 ideas

4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / b. Terminology of PL
9540 A 'value-assignment' (V) is when to each variable in the set V assigns either the value 1 or the value 0 [Hughes/Cresswell]
4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / d. Basic theorems of PL
9541 The Law of Transposition says (P→Q) → (¬Q→¬P) [Hughes/Cresswell]
4. Formal Logic / B. Propositional Logic PL / 4. Soundness of PL
9543 The rules preserve validity from the axioms, so no thesis negates any other thesis [Hughes/Cresswell]
4. Formal Logic / F. Set Theory ST / 3. Types of Set / b. Empty (Null) Set
21548 The null class is the class with all the non-existents as its members [MacColl, by Lackey]
5. Theory of Logic / K. Features of Logics / 4. Completeness
9544 A system is 'weakly' complete if all wffs are derivable, and 'strongly' if theses are maximised [Hughes/Cresswell]
5. Theory of Logic / K. Features of Logics / 7. Decidability
18758 Validity is provable, but invalidity isn't, because the model is infinite [Church, by McGee]