16 ideas
| 8226 | A well-posed problem is a problem solved [Bergson, by Deleuze/Guattari] |
| Full Idea: Bergson said that a well-posed problem was a problem solved | |
| From: report of Henri Bergson (works [1910]) by G Deleuze / F Guattari - What is Philosophy? 1.3 | |
| A reaction: This is fairly well in tune with the logical positivist style of philosophising, which tends to ask "what exactly is the question?" rather more than it asks "what is the answer?". I thoroughly approve of both of them (e.g. on free will). |
| 13838 | A decent modern definition should always imply a semantics [Hacking] |
| Full Idea: Today we expect that anything worth calling a definition should imply a semantics. | |
| From: Ian Hacking (What is Logic? [1979], §10) | |
| A reaction: He compares this with Gentzen 1935, who was attempting purely syntactic definitions of the logical connectives. |
| 13833 | 'Thinning' ('dilution') is the key difference between deduction (which allows it) and induction [Hacking] |
| Full Idea: 'Dilution' (or 'Thinning') provides an essential contrast between deductive and inductive reasoning; for the introduction of new premises may spoil an inductive inference. | |
| From: Ian Hacking (What is Logic? [1979], §06.2) | |
| A reaction: That is, inductive logic (if there is such a thing) is clearly non-monotonic, whereas classical inductive logic is monotonic. |
| 13834 | Gentzen's Cut Rule (or transitivity of deduction) is 'If A |- B and B |- C, then A |- C' [Hacking] |
| Full Idea: If A |- B and B |- C, then A |- C. This generalises to: If Γ|-A,Θ and Γ,A |- Θ, then Γ |- Θ. Gentzen called this 'cut'. It is the transitivity of a deduction. | |
| From: Ian Hacking (What is Logic? [1979], §06.3) | |
| A reaction: I read the generalisation as 'If A can be either a premise or a conclusion, you can bypass it'. The first version is just transitivity (which by-passes the middle step). |
| 13835 | Only Cut reduces complexity, so logic is constructive without it, and it can be dispensed with [Hacking] |
| Full Idea: Only the cut rule can have a conclusion that is less complex than its premises. Hence when cut is not used, a derivation is quite literally constructive, building up from components. Any theorem obtained by cut can be obtained without it. | |
| From: Ian Hacking (What is Logic? [1979], §08) |
| 13845 | The various logics are abstractions made from terms like 'if...then' in English [Hacking] |
| Full Idea: I don't believe English is by nature classical or intuitionistic etc. These are abstractions made by logicians. Logicians attend to numerous different objects that might be served by 'If...then', like material conditional, strict or relevant implication. | |
| From: Ian Hacking (What is Logic? [1979], §15) | |
| A reaction: The idea that they are 'abstractions' is close to my heart. Abstractions from what? Surely 'if...then' has a standard character when employed in normal conversation? |
| 13840 | First-order logic is the strongest complete compact theory with Löwenheim-Skolem [Hacking] |
| Full Idea: First-order logic is the strongest complete compact theory with a Löwenheim-Skolem theorem. | |
| From: Ian Hacking (What is Logic? [1979], §13) |
| 13844 | A limitation of first-order logic is that it cannot handle branching quantifiers [Hacking] |
| Full Idea: Henkin proved that there is no first-order treatment of branching quantifiers, which do not seem to involve any idea that is fundamentally different from ordinary quantification. | |
| From: Ian Hacking (What is Logic? [1979], §13) | |
| A reaction: See Hacking for an example of branching quantifiers. Hacking is impressed by this as a real limitation of the first-order logic which he generally favours. |
| 13842 | Second-order completeness seems to need intensional entities and possible worlds [Hacking] |
| Full Idea: Second-order logic has no chance of a completeness theorem unless one ventures into intensional entities and possible worlds. | |
| From: Ian Hacking (What is Logic? [1979], §13) |
| 13837 | With a pure notion of truth and consequence, the meanings of connectives are fixed syntactically [Hacking] |
| Full Idea: My doctrine is that the peculiarity of the logical constants resides precisely in that given a certain pure notion of truth and consequence, all the desirable semantic properties of the constants are determined by their syntactic properties. | |
| From: Ian Hacking (What is Logic? [1979], §09) | |
| A reaction: He opposes this to Peacocke 1976, who claims that the logical connectives are essentially semantic in character, concerned with the preservation of truth. |
| 13839 | Perhaps variables could be dispensed with, by arrows joining places in the scope of quantifiers [Hacking] |
| Full Idea: For some purposes the variables of first-order logic can be regarded as prepositions and place-holders that could in principle be dispensed with, say by a system of arrows indicating what places fall in the scope of which quantifier. | |
| From: Ian Hacking (What is Logic? [1979], §11) | |
| A reaction: I tend to think of variables as either pronouns, or as definite descriptions, or as temporary names, but not as prepositions. Must address this new idea... |
| 13843 | If it is a logic, the Löwenheim-Skolem theorem holds for it [Hacking] |
| Full Idea: A Löwenheim-Skolem theorem holds for anything which, on my delineation, is a logic. | |
| From: Ian Hacking (What is Logic? [1979], §13) | |
| A reaction: I take this to be an unusually conservative view. Shapiro is the chap who can give you an alternative view of these things, or Boolos. |
| 22692 | A work can be morally and artistically excellent, despite rejecting moral truth [John,E] |
| Full Idea: A work that rejects moral truth can be artistically excellent, in part because of its moral content. | |
| From: Eileen John (Artistic Value and Opportunistic Moralism [2006], Intr) | |
| A reaction: She cites the film 'Trainspotting', about desperate drug addicts, because it gives an amoral insight into their world. |
| 22693 | The works we value most are in sympathy with our own moral views [John,E] |
| Full Idea: The works we tend to value most highly are ones that are in sympathy with the moral views we actually accept. | |
| From: Eileen John (Artistic Value and Opportunistic Moralism [2006], Intro) | |
| A reaction: I would have to endorse this. She admits that we may rate other works very highly, but they won't appear on our list of favourites. This fact may well distort philosophical discussions of morality and art. |
| 22694 | We should understand what is morally important in a story, without having to endorse it [John,E] |
| Full Idea: Our responses to literature should show that we grasp whatever counts as morally important within the narrative, but not necessarily that we judge and feel in the way deemed appropriate by the work. | |
| From: Eileen John (Artistic Value and Opportunistic Moralism [2006], 'Accommodating') | |
| A reaction: She gives as an example a story by Hemingway which places a high value on the courageous hunting of big game. A second example is the total amorality of a Highsmith novel. This idea seems exactly right to me. |
| 22695 | We value morality in art because that is what we care about - but it is a contingent fact [John,E] |
| Full Idea: Moral value is valuable in art because people care about moral value. This runs deep, but it is a contingent matter, and the value of morality in art hinges on art's need to provide something precious to us. | |
| From: Eileen John (Artistic Value and Opportunistic Moralism [2006], 'Contingency') | |
| A reaction: I think this is exactly right. Thrillers are written with very little moral concern, for a readership which cares about brave and exciting deeds. Even there, violence has its ethics. |