9 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. |
| 13163 | Circles must be bounded, so cannot be infinite [Leibniz] |
| Full Idea: An infinite circle is impossible, since any circle is bounded by its circumference. | |
| From: Gottfried Leibniz (Dialogue on human freedom and origin of evil [1695], p.114) | |
| A reaction: This is interesting if one is asking what the essence of a circle must be. If is tempting to say merely that the radii must be equal, but can they have the length of some vast transfinite number? The circumference must be 2π bigger. |
| 13162 | Sloth's Syllogism: either it can't happen, or it is inevitable without my effort [Leibniz] |
| Full Idea: The ancient Sloth's Syllogism says that if something is foreseen and infallible, it will happen without my effort, and if it is not foreseen, it will not happen, even though I am able to do it. | |
| From: Gottfried Leibniz (Dialogue on human freedom and origin of evil [1695], p.113) | |
| A reaction: Presumable the foreseeing is to be done by the oracle, and not by the slothful person. |
| 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). |
| 16697 | Time is independent of motion, because God could stop everything for a short or long time [Crathorn, by Pasnau] |
| Full Idea: Suppose God annihilates everything, and then creates something new. The vacant interval could last a shorter or longer time, so there are facts about time independent of facts about motion. | |
| From: report of William Crathorn (Sentences [1335], I.16, concl.2) by Robert Pasnau - Metaphysical Themes 1274-1671 18.2 | |
| A reaction: Not very persuasive if God is in some way 'timeless'. Crathorn would have loved Shoemaker's argument, where motionless time is the best explanation, rather than a possible explanation. |
| 19339 | Evil is a negation of good, which arises from non-being [Leibniz] |
| Full Idea: The cause of good is positive, but evil is a defect, that is, a privation or negation, and consequently, it arises from nothingness or nonbeing. | |
| From: Gottfried Leibniz (Dialogue on human freedom and origin of evil [1695], p.114) | |
| A reaction: He goes on to illustrate his idea from mathematics. He is modifying Augustine's view that evil is an absence of good, by adding nonbeing as the driving force behind it. Doesn't sound very persuasive to me. |
| 13164 | God only made sin possible because a much greater good can be derived from it [Leibniz] |
| Full Idea: We must believe that God would not have allowed sin nor would he have created things he knows will sin, if he could not derive from them a good incomparably greater than the resulting evil. | |
| From: Gottfried Leibniz (Dialogue on human freedom and origin of evil [1695], p.115) | |
| A reaction: Why 'must' we believe this? Do we have to imagine all the genocides shrinking to insignificance once we grasp the wonderful goods that can be derived from them? The end justifies the means. Genocide is actually a good thing. Hm. |