10 ideas
11211 | If a sound conclusion comes from two errors that cancel out, the path of the argument must matter [Rumfitt] |
Full Idea: If a designated conclusion follows from the premisses, but the argument involves two howlers which cancel each other out, then the moral is that the path an argument takes from premisses to conclusion does matter to its logical evaluation. | |
From: Ian Rumfitt ("Yes" and "No" [2000], II) | |
A reaction: The drift of this is that our view of logic should be a little closer to the reasoning of ordinary language, and we should rely a little less on purely formal accounts. |
11210 | Standardly 'and' and 'but' are held to have the same sense by having the same truth table [Rumfitt] |
Full Idea: If 'and' and 'but' really are alike in sense, in what might that likeness consist? Some philosophers of classical logic will reply that they share a sense by virtue of sharing a truth table. | |
From: Ian Rumfitt ("Yes" and "No" [2000]) | |
A reaction: This is the standard view which Rumfitt sets out to challenge. |
11212 | The sense of a connective comes from primitively obvious rules of inference [Rumfitt] |
Full Idea: A connective will possess the sense that it has by virtue of its competent users' finding certain rules of inference involving it to be primitively obvious. | |
From: Ian Rumfitt ("Yes" and "No" [2000], III) | |
A reaction: Rumfitt cites Peacocke as endorsing this view, which characterises the logical connectives by their rules of usage rather than by their pure semantic value. |
10632 | The real numbers may be introduced by abstraction as ratios of quantities [Hale, by Hale/Wright] |
Full Idea: The real numbers may be introduced by abstraction as ratios of quantities. ..They are not defined by Dedekind cuts; rather, the cuts constitute a domain with the properties that are a necessary precondition. | |
From: report of Bob Hale (Reals by Abstraction [1998]) by B Hale / C Wright - Intro to 'The Reason's Proper Study' 3.3 | |
A reaction: This is Hale's neo-logicist attempt to derive the real numbers from Hume's Principle. |
11214 | We learn 'not' along with affirmation, by learning to either affirm or deny a sentence [Rumfitt] |
Full Idea: The standard view is that affirming not-A is more complex than affirming the atomic sentence A itself, with the latter determining its sense. But we could learn 'not' directly, by learning at once how to either affirm A or reject A. | |
From: Ian Rumfitt ("Yes" and "No" [2000], IV) | |
A reaction: [compressed] This seems fairly anti-Fregean in spirit, because it looks at the psychology of how we learn 'not' as a way of clarifying what we mean by it, rather than just looking at its logical behaviour (and thus giving it a secondary role). |
22445 | Morality shows murder is wrong, but not what counts as a murder [Foot] |
Full Idea: While one can determine from the concept of morality that there is an objection to murder one cannot determine completely what will count as murder. | |
From: Philippa Foot (Morality and Art [1972], p.7) | |
A reaction: She then refers to abortion, but there are military and criminal problem cases, and killings by neglect or side effect. |
22444 | A moral system must deal with the dangers and benefits of life [Foot] |
Full Idea: A moral system seems necessarily to be one aimed at removing particular dangers and securing certain benefits. | |
From: Philippa Foot (Morality and Art [1972], p.6) | |
A reaction: I thoroughly approve of this approach to morality, which anchors it in real life, rather than in ideals or principles of reason. |
22447 | Saying something 'just is' right or wrong creates an illusion of fact and objectivity [Foot] |
Full Idea: When we say that something 'just is' right or wrong we want to give the impression of some kind of fact or authority standing behind our words, ...maintaining the trappings of objectivity though the substance is not there. | |
From: Philippa Foot (Morality and Art [1972], p.9) | |
A reaction: Foot favours the idea that such a claim must depend on reasons, and that the reasons arise out of actual living. She's right. |
22448 | We sometimes just use the word 'should' to impose a rule of conduct on someone [Foot] |
Full Idea: It would be more honest to recognise that the 'should' of moral judgement is sometimes merely an instrument by which we (for our own very good reasons) try to impose a rule of conduct even on the uncaring man? | |
From: Philippa Foot (Morality and Art [1972], p.18) | |
A reaction: This is a good example, I think, of the ordinary language tradition that Foot grew up in. We load a word like 'should' with a mystical power, but the situations in which it is actually used bring us back down to earth. |
22446 | In the case of something lacking independence, calling it a human being is a matter of choice [Foot] |
Full Idea: In the problem of abortion there is a genuine choice as to whether or not to count as a human being, with the rights of a human being, what would become a human being but is not yet capable of independent life. | |
From: Philippa Foot (Morality and Art [1972], p.7) | |
A reaction: There must be some basis for the choice. We can't call a dead person a human being. Choosing to call a tiny zygote a human being seems very implausible. Pre-viability strikes me as implausible. |