7 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. |
| 12735 | Everything has a fixed power, as required by God, and by the possibility of reasoning [Leibniz] |
| Full Idea: It follows from the nature of God that there is a fixed power of a definite magnitude [non vagam] in anything whatsoever, otherwise there would be no reasonings about those things. | |
| From: Gottfried Leibniz (De aequopollentia causae et effectus [1679], A6.4.1964), quoted by Daniel Garber - Leibniz:Body,Substance,Monad 6 | |
| A reaction: This is double-edged. On the one hand there is the grand claim that the principle derives from divine nature, but on the other it derives from our capacity to reason and explain. No one doubts that powers are 'fixed'. |
| 22137 | Observation can force rejection of some part of the initial set of claims [Duhem, by Boulter] |
| Full Idea: Logic and observation alone do not force a scientist to reject a scientific claim if experimental observations so not turn out as expected. The scientist must reject something of the initial set of claims, but that is a matter of choice. | |
| From: report of Pierre Duhem (The Aim and Structure of Physical Theory [1906]) by Stephen Boulter - Why Medieval Philosophy Matters 2 | |
| A reaction: This is a key point against any simplified Popperian notion of falsification. Tiny observations can't kill huge well supported theories. |
| 18197 | Experiments only test groups of hypotheses, and can't show which one is wrong [Duhem] |
| Full Idea: The physicist can never subject an isolated hypothesis to experimental test, but only a whole group of hypotheses; when the experiment is in disagreement with his predictions ...it does not designate which one should be changed. | |
| From: Pierre Duhem (The Aim and Structure of Physical Theory [1906], p.187), quoted by Penelope Maddy - Naturalism in Mathematics II.2 | |
| A reaction: This is the idea frequently invoked by Quine, in support of his holistic view of scientific knowledge (along with Neurath's Boat). |
| 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). |