8 ideas
| 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'. |
| 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. |
| 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] |
| 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] |
| 8510 | 'Socrates is wise' means a concurrence sum contains a member of a similarity set [Williams,DC] |
| Full Idea: 'Socrates is wise' means that the concurrence sum (Socrates) includes a trope which is a member of the similarity set (Wisdom). | |
| From: Donald C. Williams (On the Elements of Being: I [1953], p.119) | |
| A reaction: Resemblance has to be taken as a basic (and presumably unanalysable) concept, which invites Russell's objection (Idea 4441). |
| 8508 | A 'trope' is an abstract particular, the occurrence of an essence [Williams,DC] |
| Full Idea: I shall divert the word 'trope' to stand for the abstract particular which is, so to speak, the occurrence of an essence. | |
| From: Donald C. Williams (On the Elements of Being: I [1953], p.115) | |
| A reaction: Thus tropes entered philosophical discussion. Presumably the precedent for an 'abstract particular' would be a particular occurrence of the number 7. |
| 8509 | A world is completely constituted by its tropes and their connections [Williams,DC] |
| Full Idea: Any possible world, and hence, of course, this one, is completely constituted by its tropes and connections of location and similarity. | |
| From: Donald C. Williams (On the Elements of Being: I [1953], p.116) | |
| A reaction: Note that Williams regularly referred to possible worlds in 1953. This is a full-blooded trope theory, which asserts that objects are bundles of tropes, so that both particulars and universals are ontologically taken care of. |
| 21006 | If women share rights with men, they will exhibit similar virtues [Wollstonecraft] |
| Full Idea: Let woman share the rights and she will emulate the virtues of man; for she must grow more perfect when emancipated, or justify that authority that chains such a weak being to her duty. | |
| From: Mary Wollstonecraft (Vindication of the Rights of Women [1792], p.294), quoted by Amartya Sen - The Idea of Justice 18 'Wrath' | |
| A reaction: Presumably this implies that if emancipation led to women exceeding men in such virtues, there would be some justification for imposing the chains on the men rather than the women. Consider wars. Probably best to just abandon chains. |