Combining Texts

All the ideas for 'Clitophon', 'Problems in the Explanation of Action' 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]
     Full Idea: A 'value-assignment' (V) is when to each variable in the set V assigns either the value 1 or the value 0.
     From: GE Hughes/M Cresswell (An Introduction to Modal Logic [1968], Ch.1)
     A reaction: In the interpreted version of the logic, 1 and 0 would become T (true) and F (false). The procedure seems to be called nowadays a 'valuation'.
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]
     Full Idea: The Law of Transposition says that (P→Q) → (¬Q→¬P).
     From: GE Hughes/M Cresswell (An Introduction to Modal Logic [1968], Ch.1)
     A reaction: That is, if the consequent (Q) of a conditional is false, then the antecedent (P) must have been false.
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]
     Full Idea: An axiomatic system is most naturally consistent iff no thesis is the negation of another thesis. It can be shown that every axiom is valid, that the transformation rules are validity-preserving, and if a wff α is valid, then ¬α is not valid.
     From: GE Hughes/M Cresswell (An Introduction to Modal Logic [1968], Ch.1)
     A reaction: [The labels 'soundness' and 'consistency' seem interchangeable here, with the former nowadays preferred]
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]
     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.
     From: GE Hughes/M Cresswell (An Introduction to Modal Logic [1968], Ch.1)
     A reaction: [They go on to say that Propositional Logic is strongly complete, but Modal Logic is not]
20. Action / B. Preliminaries of Action / 1. Intention to Act / b. Types of intention
20074 We can keep Davidson's account of intentions in action, by further explaining prior intentions [Davidson, by Stout,R]
     Full Idea: Davidson's original account of intentions might still stand if we could accept that prior intentions are different in kind from intentions with which one acts.
     From: report of Donald Davidson (Problems in the Explanation of Action [1987]) by Rowland Stout - Action 8 'Davidson's'
     A reaction: Davidson says prior intention is all-out judgement of desirability. Prior intentions are more deliberate, with the other intentions as a presumed background to action. Compare Sartre's dual account of the self.
22. Metaethics / B. Value / 2. Values / f. Altruism
1590 The just man does not harm his enemies, but benefits everyone [Plato]
     Full Idea: First, Socrates, you told me justice is harming your enemies and helping your friends. But later it seemed that the just man, since everything he does is for someone's benefit, never harms anyone.
     From: Plato (Clitophon [c.372 BCE], 410b)
     A reaction: Socrates certainly didn't subscribe to the first view, which is the traditional consensus in Greek culture. In general Socrates agreed with the views later promoted by Jesus.