10 ideas
| 11022 | Gentzen introduced a natural deduction calculus (NK) in 1934 [Gentzen, by Read] |
| Full Idea: Gentzen introduced a natural deduction calculus (NK) in 1934. | |
| From: report of Gerhard Gentzen (works [1938]) by Stephen Read - Thinking About Logic Ch.8 |
| 11065 | The inferential role of a logical constant constitutes its meaning [Gentzen, by Hanna] |
| Full Idea: Gentzen argued that the inferential role of a logical constant constitutes its meaning. | |
| From: report of Gerhard Gentzen (works [1938]) by Robert Hanna - Rationality and Logic 5.3 | |
| A reaction: Possibly inspired by Wittgenstein's theory of meaning as use? This idea was the target of Prior's famous connective 'tonk', which has the role of implying anything you like, proving sentences which are not logical consequences. |
| 11023 | The logical connectives are 'defined' by their introduction rules [Gentzen] |
| Full Idea: The introduction rules represent, as it were, the 'definitions' of the symbols concerned, and the elimination rules are no more, in the final analysis, than the consequences of these definitions. | |
| From: Gerhard Gentzen (works [1938]), quoted by Stephen Read - Thinking About Logic Ch.8 | |
| A reaction: If an introduction-rule (or a truth table) were taken as fixed and beyond dispute, then it would have the status of a definition, since there would be nothing else to appeal to. So is there anything else to appeal to here? |
| 11213 | Each logical symbol has an 'introduction' rule to define it, and hence an 'elimination' rule [Gentzen] |
| Full Idea: To every logical symbol there belongs precisely one inference figure which 'introduces' the symbol ..and one which 'eliminates' it. The introductions represent the 'definitions' of the symbols concerned, and eliminations are consequences of these. | |
| From: Gerhard Gentzen (works [1938], II.5.13), quoted by Ian Rumfitt - "Yes" and "No" III | |
| A reaction: [1935 paper] This passage is famous, in laying down the basics of natural deduction systems of logic (ones using only rules, and avoiding axioms). Rumfitt questions whether Gentzen's account gives the sense of the connectives. |
| 10067 | Gentzen proved the consistency of arithmetic from assumptions beyond arithmetic [Gentzen, by Musgrave] |
| Full Idea: Gentzen proved the consistency of arithmetic from assumptions which transcend arithmetic. | |
| From: report of Gerhard Gentzen (works [1938]) by Alan Musgrave - Logicism Revisited §5 | |
| A reaction: This does not contradict Gödel's famous result, but reinforces it. The interesting question is what assumptions Gentzen felt he had to make. |
| 22330 | Grice said patterns of use are often semantically irrelevant, because it is a pragmatic matter [Grice, by Glock] |
| Full Idea: The slogan that meaning is use came under scrutiny by Grice's theory of conversational implicature. He said patterns of use shown in analysis were often semantically irrelevant, snce they are due not meanings of expressions but to pragmatic principles. | |
| From: report of H. Paul Grice (Some Models for Implicature [1967]) by Hans-Johann Glock - What is Analytic Philosophy? 2.8 | |
| A reaction: I think the simplest objection is that words only have use because they have a meaning; The most interesting part of pragmatics is what you DON'T say in conversation. |
| 18045 | Grice's maxim of quality says do not assert what you believe to be false [Grice, by Magidor] |
| Full Idea: Grice's maxim of quality says one ought not to assert what one believes to be false. | |
| From: report of H. Paul Grice (Some Models for Implicature [1967]) by Ofra Magidor - Category Mistakes 5.2 | |
| A reaction: The obvious exception is irony, where are truth is asserted, but the listener is supposed to spot that you are not really asserting it. |
| 18044 | Grice's maxim of manner requires one to be as brief as possible [Grice, by Magidor] |
| Full Idea: Grice's maxim of manner requires one to be as brief as possible. | |
| From: report of H. Paul Grice (Some Models for Implicature [1967]) by Ofra Magidor - Category Mistakes 5.2 | |
| A reaction: An alternative maxim of conversation is that there should not be long silences between contributions - which would probably result if the contributions are all curtly abbreviated. |
| 18046 | Grice's maxim of quantity says be sufficiently informative [Grice, by Magidor] |
| Full Idea: Grice's maxim of quantity says 'make your contributions as informative as required'. | |
| From: report of H. Paul Grice (Some Models for Implicature [1967]) by Ofra Magidor - Category Mistakes 5.2 | |
| A reaction: Is the 'requirement' of informative for the speaker or for the listener? It is easy to image situations where, one way or the other, the two people don't agree about informativenss. |
| 22393 | I don't understand the idea of a reason for acting, but it is probably the agent's interests or desires [Foot] |
| Full Idea: I am sure I do not understand the idea of a reason for acting, and I wonder whether anyone else does either. I incline to the view that all such reasons depend either on the agent's interests (meaning here what is in his interest) or else on his desires. | |
| From: Philippa Foot (Reasons for Actions and Desires [1972], p.156 Post) | |
| A reaction: It seems common to assume that a reason for an action must be something rational, but it makes sense to say that the reason for someone's action was an irrational whim. Is the reason for an action just the cause of the action? |