9 ideas
| 7791 | The simplest of the logics based on possible worlds is Lewis's S5 [Lewis,CI, by Girle] |
| Full Idea: C.I.Lewis constructed five axiomatic systems of modal logic, and named them S1 to S5. It turns out that the simplest of the logics based on possible worlds is the same as Lewis's S5. | |
| From: report of C.I. Lewis (works [1935]) by Rod Girle - Modal Logics and Philosophy 2.1 | |
| A reaction: Nathan Salmon ('Reference and Essence' 2nd ed) claims (on p.xvii) that "the correct modal logic is weaker than S5 and weaker even than S4". Which is the greater virtue, simplicity or weakness? |
| 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. |
| 16083 | Aristotelian matter seriously threatens the intrinsic unity and substantiality of its object [Gill,ML] |
| Full Idea: On the interpretation of Aristotelian matter that I shall propose, matter seriously threatens the intrinsic unity, and hence the substantiality, of the object to which it contributes. | |
| From: Mary Louise Gill (Aristotle on Substance [1989], Intro) | |
| A reaction: Presumably the thought is that if an object is form+matter (hylomorphism), then forms are essentially unified, but matter is essentially unified and sloppy. |
| 11002 | Equating necessity with informal provability is the S4 conception of necessity [Lewis,CI, by Read] |
| Full Idea: C.I.Lewis's S4 system develops a sense of necessity as 'provability' in some fairly informal sense. | |
| From: report of C.I. Lewis (works [1935]) by Stephen Read - Thinking About Logic Ch. 4 |
| 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). |
| 17006 | Prime matter has no place in Aristotle's theories, and passages claiming it are misread [Gill,ML] |
| Full Idea: I argue that prime matter has no place in Aristotle's elemental theory. ..References to prime matter are found in Aristotle's work because his theory was thought to need the doctrine. If I am right, these passages will all admit of another interpretation. | |
| From: Mary Louise Gill (Aristotle on Substance [1989], App) | |
| A reaction: If correct, this strikes me as important for the history of ideas, because scholastics got themselves in a right tangle over prime matter. See Pasnau on it. It pushed the 17th century into corpuscularianism. |
| 16093 | Prime matter is actually nothing and potentially everything (or potentially an element) [Gill,ML] |
| Full Idea: Prime matter is supposed to be actually nothing and potentially everything or, at any rate, potentially the simplest bodies - earth, water, air and fire. | |
| From: Mary Louise Gill (Aristotle on Substance [1989], Ch.1) | |
| A reaction: The view that the four elements turn out to be prime matter is distinctive of Gill's approach. Prime matter sounds like quark soup in the early universe. |