10 ideas
| 22764 | Ordinary speech is not exact about what is true; we say we are digging a well before the well exists [Sext.Empiricus] |
| Full Idea: We must allow ordinary speech to use inexact terms, as it does not seek after what is really true but what is supposed to be true. We speak of digging a well or weaving a cloak, but there is no well or cloak when they are being dug or woven. | |
| From: Sextus Empiricus (Against the Logicians (two books) [c.180], II.129) | |
| A reaction: Nice examples. The imprecision is reduced if I say I am creating a well, because that implies something that is not yet complete. If I say I intend to dig a well, is that imprecise because the well does not exist? |
| 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. |
| 22762 | Some properties are inseparable from a thing, such as the length, breadth and depth of a body [Sext.Empiricus] |
| Full Idea: Some properties are inseparable from the things to which they belong - as are length, breadth and depth from bodies, for without their presence it is impossible to perceive Body. | |
| From: Sextus Empiricus (Against the Logicians (two books) [c.180], I.270) | |
| A reaction: For the opposite case he suggests a man running, talking or sleeping. He doesn't mention essential natures, but this is clearly correct. We might say that they are properties which need to be mentioned in a full definition. |
| 22759 | Fools, infants and madmen may speak truly, but do not know [Sext.Empiricus] |
| Full Idea: The fool and the infant and the madman at times say something true, but they do not possess knowledge of the true. | |
| From: Sextus Empiricus (Against the Logicians (two books) [c.180], I.042) | |
| A reaction: This may be correct of someone who is insane, but seems unfair to the fool and the infant. At what age do children begin to know things? If speech was just random nonsense, an accidental truth seems impossible. |
| 22760 | Madmen are reliable reporters of what appears to them [Sext.Empiricus] |
| Full Idea: The madman is a trustworthy criterion of the appearances which occur in madness. | |
| From: Sextus Empiricus (Against the Logicians (two books) [c.180], I.062) | |
| A reaction: It is hard to conceive of an genuinely insane person deliberately misreporting their hallucinations. They are, of course, the sole witness. |
| 22763 | We can only dream of a winged man if we have experienced men and some winged thing [Sext.Empiricus] |
| Full Idea: He who in his sleep dreams of a winged man does not dream so without having seen some winged thing and a man. And in general it is impossible to find in conception anything which one does not possess as known by experience. | |
| From: Sextus Empiricus (Against the Logicians (two books) [c.180], II.058) | |
| A reaction: This precisely David Hume's empiricist account of the formation of concepts. Hume's example is a golden mountain, which he got from Aquinas. How do we dream of faces we have never encountered, or shapes we have never seen? |
| 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). |
| 3804 | Darwin's idea was the best idea ever [Dennett] |
| Full Idea: If I were to give an award for the single best idea anyone has ever had, I'd give it to Darwin. | |
| From: Daniel C. Dennett (Darwin's Dangerous Idea [1995], §1.1) |