16 ideas
| 14352 | '¬', '&', and 'v' are truth functions: the truth of the compound is fixed by the truth of the components [Jackson] |
| Full Idea: It is widely agreed that '¬', '&', and 'v' are 'truth functions': the truth value of a compound sentence formed using them is fully determined by the truth value or values of the component sentences. | |
| From: Frank Jackson (Conditionals [2006], 'Equiv') | |
| A reaction: A candidate for not being a truth function might be a conditional →, where the arrow adds something over and above the propositions it connects. The relationship has an additional truth value? Does A depend on B? |
| 14360 | Possible worlds for subjunctives (and dispositions), and no-truth for indicatives? [Jackson] |
| Full Idea: Subjunctive conditionals are intimately connected with dispositional properties and causation. ...Consequently, a position some find attractive is that possible worlds theory applies to subjunctives, while the no-truth theory applies to indicatives. | |
| From: Frank Jackson (Conditionals [2006], 'Indicative') | |
| A reaction: My intuitions are to reject this and favour a unified account, where both sorts of conditionals are mappings of the relationships among the facts of actuality. Nice slogan! |
| 14353 | Modus ponens requires that A→B is F when A is T and B is F [Jackson] |
| Full Idea: Modus ponens is intuitively valid, but in A,A→B|B if A is true and B is false that must be because A→B is false. So A→B is false when A is true and B is false. | |
| From: Frank Jackson (Conditionals [2006], 'Equiv') | |
| A reaction: This is his first step in showing how the truth functional account of A→B acquires its truth table. If you are giving up the truth functional view of conditionals, presumably you are not also going to give up modus ponens? |
| 14354 | When A and B have the same truth value, A→B is true, because A→A is a logical truth [Jackson] |
| Full Idea: (A→A) is a logical truth, so some conditionals with antecedent and consequent the same truth value are true. But if '→' is a truth function, that will be true for all cases. Hence whenever A and B are alike in truth value, (A→B) is true. | |
| From: Frank Jackson (Conditionals [2006], 'Equiv') | |
| A reaction: His second step in demonstrating the truth table for →, assuming it is truth functional. |
| 14355 | (A&B)→A is a logical truth, even if antecedent false and consequent true, so it is T if A is F and B is T [Jackson] |
| Full Idea: (A&B)→A is a logical truth, but A can be true and B false, so that (A&B) is false. So some conditionals with false antecedent and true consequent are true. If → is a truth function, then whenever A is false and B is true (A→B) is true. | |
| From: Frank Jackson (Conditionals [2006], 'Equiv') | |
| A reaction: This is his third and final step in showing the truth table of → if it is truth functional. |
| 14358 | In the possible worlds account of conditionals, modus ponens and modus tollens are validated [Jackson] |
| Full Idea: In the possible worlds account modus ponens is validated (the closest world, the actual, is a B-world just if B is true), and modus tollens is validated (if B is false, the actual world is not an A-world, so A is false). | |
| From: Frank Jackson (Conditionals [2006], 'Famous') | |
| A reaction: [see Jackson for slightly fuller versions] This looks like a minimal requirement for a decent theory of conditionals, so Jackson explains the attractions of the possible worlds view very persuasively. |
| 14359 | Only assertions have truth-values, and conditionals are not proper assertions [Jackson] |
| Full Idea: In the no-truth theory of conditionals they have justified assertion or acceptability conditions but not truth conditions. ...The motivation is that only assertions have truth values, and conditionals are arguments, not proper assertions. | |
| From: Frank Jackson (Conditionals [2006], 'No-truth') | |
| A reaction: Once I trim this idea down to its basics, it suddenly looks very persuasive. Except that I am inclined to think that conditional truths do state facts about the world - perhaps as facts about how more basic truths are related to each other. |
| 14357 | Possible worlds account, unlike A⊃B, says nothing about when A is false [Jackson] |
| Full Idea: In the possible worlds account of conditionals A⊃B is not sufficient for A→B. If A is false then A⊃B is true, but here nothing is implied about whether the world most like the actual world except that A is true is or is not a B-world. | |
| From: Frank Jackson (Conditionals [2006], 'Possible') | |
| A reaction: The possible worlds account seems to be built on Ramsey's idea of just holding A true and seeing what you get. Being committed to B being automatically true if A is false seems highly counterintuitive. |
| 14356 | We can't insist that A is relevant to B, as conditionals can express lack of relevance [Jackson] |
| Full Idea: One addition to the truth functional account of conditionals is that A be somehow relevant to B. However, sometimes we use conditionals to express lack of relevance, as in 'If Fred works he will fail, and if Fred doesn't work he will fail'. | |
| From: Frank Jackson (Conditionals [2006], 'Possible') | |
| A reaction: This certainly seems to put paid to an attractive instant solution to the problem. |
| 12608 | Concepts are distinguished by roles in judgement, and are thus tied to rationality [Peacocke] |
| Full Idea: 'Concept' is a notion tied, in the classical Fregean manner, to cognitive significance. Concepts are distinct if we can judge rationally of one, without the other. Concepts are constitutively and definitionally tied to rationality in this way. | |
| From: Christopher Peacocke (Truly Understood [2008], 2.2) | |
| A reaction: It seems to a bit optimistic to say, more or less, that thinking is impossible if it isn't rational. Rational beings have been selected for. As Quine nicely observed, duffers at induction have all been weeded out - but they may have existed, briefly. |
| 16383 | Puzzled Pierre has two mental files about the same object [Recanati on Kripke] |
| Full Idea: In Kripke's puzzle about belief, the subject has two distinct mental files about one and the same object. | |
| From: comment on Saul A. Kripke (A Puzzle about Belief [1979]) by François Recanati - Mental Files 17.1 | |
| A reaction: [Pierre distinguishes 'London' from 'Londres'] The Kripkean puzzle is presented as very deep, but I have always felt there was a simple explanation, and I suspect that this is it (though I will leave the reader to think it through, as I'm very busy…). |
| 12605 | A sense is individuated by the conditions for reference [Peacocke] |
| Full Idea: My basic Fregean idea is that a sense is individuated by the fundamental condition for something to be its reference. | |
| From: Christopher Peacocke (Truly Understood [2008], Intro) | |
| A reaction: For something to actually be its reference (as opposed to imagined reference), truth must be involved. This needs the post-1891 Frege view of such things, and not just the view of concepts as functions which he started with. |
| 12607 | Fregean concepts have their essence fixed by reference-conditions [Peacocke] |
| Full Idea: The Fregean view is that the essence of a concept is given by the fundamental condition for something to be its reference. | |
| From: Christopher Peacocke (Truly Understood [2008], 2.1) | |
| A reaction: Peacocke is a supporter of the Fregean view. How does this work for concepts of odd creatures in a fantasy novel? Or for mistaken or confused concepts? For Burge's 'arthritis in my thigh'? I don't reject the Fregean view. |
| 12609 | Concepts have distinctive reasons and norms [Peacocke] |
| Full Idea: For each concept, there will be some reasons or norms distinctive of that concept. | |
| From: Christopher Peacocke (Truly Understood [2008], 2.3) | |
| A reaction: This is Peacocke's bold Fregean thesis (and it sounds rather Kantian to me). I dislike the word 'norms' (long story), but reasons are interesting. The trouble is the distinction between being a reason for something (its cause) and being a reason for me. |
| 12604 | Any explanation of a concept must involve reference and truth [Peacocke] |
| Full Idea: For some particular concept, we can argue that some of its distinctive features are adequately explained only by a possession-condition that involves reference and truth essentially. | |
| From: Christopher Peacocke (Truly Understood [2008], Intro) | |
| A reaction: He reached this view via the earlier assertion that it is the role in judgement which key to understanding concepts. I like any view of such things which says that truth plays a role. |
| 12610 | Encountering novel sentences shows conclusively that meaning must be compositional [Peacocke] |
| Full Idea: The phenomenon of understanding sentences one has never encountered before is decisive against theories of meaning which do not proceed compositionally. | |
| From: Christopher Peacocke (Truly Understood [2008], 4.3) | |
| A reaction: I agree entirely. It seems obvious, as soon as you begin to slowly construct a long and unusual sentence, and follow the mental processes of the listener. |