9 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] |
| 7752 | Only the utterer's primary intention is relevant to the meaning [Grice] |
| Full Idea: Only what I may call the primary intention of an utterer is relevant to the (non-natural) meaning of an utterance. | |
| From: H. Paul Grice (Meaning [1957], p.47) | |
| A reaction: This sounds okay for simple statements, but gets really tricky with complex statements, such as very ironic remarks delivered to an audience of diverse people. |
| 7751 | Meaning needs an intention to induce a belief, and a recognition that this is the speaker's intention [Grice] |
| Full Idea: For a statement to have (non-naturally) meant something, not merely must it have been 'uttered' with the intention of inducing a certain belief, but also the utterer must have intended an 'audience' to recognise the intention behind the utterance. | |
| From: H. Paul Grice (Meaning [1957], p.43) | |
| A reaction: This is Grice's famous and distinctive theory of meaning. I am struck by the problem of a password, which seems to have a quite different intention from its literal meaning. Also a speaker with two different audiences and opposite intentions. |
| 7753 | We judge linguistic intentions rather as we judge non-linguistic intentions, so they are alike [Grice] |
| Full Idea: To show that the criteria for judging linguistic intentions are very like the criteria for judging non-linguistic intentions is to show that linguistic intentions are very like non-linguistic intentions. | |
| From: H. Paul Grice (Meaning [1957], p.48) | |
| A reaction: This hint at the end of his paper is one of the key attractions of Grice's view. It offers an account of language that fits it into the world of animal communication and evolution. It never seems to quite capture the way meaning goes beyond intentions. |
| 1748 | Archelaus was the first person to say that the universe is boundless [Archelaus, by Diog. Laertius] |
| Full Idea: Archelaus was the first person to say that the universe is boundless. | |
| From: report of Archelaus (fragments/reports [c.450 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 02.Ar.3 |
| 5989 | Archelaus said life began in a primeval slime [Archelaus, by Schofield] |
| Full Idea: Archelaus wrote that life on Earth began in a primeval slime. | |
| From: report of Archelaus (fragments/reports [c.450 BCE]) by Malcolm Schofield - Archelaus | |
| A reaction: This sounds like a fairly clearcut assertion of the production of life by evolution. Darwin's contribution was to propose the mechanism for achieving it. We should honour the name of Archelaus for this idea. |