18 ideas
| 8952 | We reach 'reflective equilibrium' when intuitions and theory completely align [Fisher] |
| Full Idea: A state of 'reflective equilibrium' is when our theory and our intuitions become completely aligned | |
| From: Jennifer Fisher (On the Philosophy of Logic [2008], 12.IV) | |
| A reaction: [Rawls made this concept famous] This is a helpful concept in trying to spell out the ideal which is the dream of believers in 'pure reason' - that there is a goal in which everything comes right. The problem is when people have different intuitions! |
| 8943 | Three-valued logic says excluded middle and non-contradition are not tautologies [Fisher] |
| Full Idea: In three-valued logic (L3), neither the law of excluded middle (p or not-p), nor the law of non-contradiction (not(p and not-p)) will be tautologies. If p has the value 'indeterminate' then so will not-p. | |
| From: Jennifer Fisher (On the Philosophy of Logic [2008], 07.I) | |
| A reaction: I quite accept that the world is full of indeterminate propositions, and that excluded middle and non-contradiction can sometimes be uncertain, but I am reluctant to accept that what is being offered here should be called 'logic'. |
| 8945 | Fuzzy logic has many truth values, ranging in fractions from 0 to 1 [Fisher] |
| Full Idea: In fuzzy logic objects have properties to a greater or lesser degree, and truth values are given as fractions or decimals, ranging from 0 to 1. Not-p is defined as 1-p, and other formula are defined in terms of maxima and minima for sets. | |
| From: Jennifer Fisher (On the Philosophy of Logic [2008], 07.II) | |
| A reaction: The question seems to be whether this is actually logic, or a recasting of probability theory. Susan Haack attacks it. If logic is the study of how truth is preserved as we move between propositions, then 0 and 1 need a special status. |
| 8951 | Classical logic is: excluded middle, non-contradiction, contradictions imply all, disjunctive syllogism [Fisher] |
| Full Idea: For simplicity, we can say that 'classical logic' amounts to the truth of four sentences: 1) either p or not-p; 2) it is not the case that both p and not-p; 3) from p and not-p, infer q; 4) from p or q and not-p, infer q. | |
| From: Jennifer Fisher (On the Philosophy of Logic [2008], 12.I) | |
| A reaction: [She says there are many ways of specifying classical logic] Intuition suggests that 2 and 4 are rather hard to dispute, while 1 is ignoring some grey areas, and 3 is totally ridiculous. There is, of course, plenty of support for 3! |
| 8950 | Logic formalizes how we should reason, but it shouldn't determine whether we are realists [Fisher] |
| Full Idea: Even if one is inclined to be a realist about everything, it is hard to see why our logic should be the determiner. Logic is supposed to formalize how we ought to reason, but whether or not we should be realists is a matter of philosophy, not logic. | |
| From: Jennifer Fisher (On the Philosophy of Logic [2008], 09.I) | |
| A reaction: Nice to hear a logician saying this. I do not see why talk in terms of an object is a commitment to its existence. We can discuss the philosopher's stone, or Arthur's sword, or the Loch Ness monster, or gravitinos, with degrees of commitment. |
| 8946 | We could make our intuitions about heaps precise with a million-valued logic [Fisher] |
| Full Idea: We could construct a 1,000,000-valued logic that would allow our intuitions concerning a heap to vary exactly with the amount of sand in the heap. | |
| From: Jennifer Fisher (On the Philosophy of Logic [2008]) | |
| A reaction: Presumably only an infinite number of grains of sand would then produce a true heap, and even one grain would count as a bit of a heap, which must both be wrong, so I can't see this helping much. |
| 8944 | Vagueness can involve components (like baldness), or not (like boredom) [Fisher] |
| Full Idea: Vague terms come in at least two different kinds: those whose constituent parts come in discrete packets (bald, rich, red) and those that don't (beauty, boredom, niceness). | |
| From: Jennifer Fisher (On the Philosophy of Logic [2008], 07.II) | |
| A reaction: The first group seem to be features of the external world, and the second all occur in the mind. Baldness may be vague, but presumably hairs are (on the whole) not. Nature doesn't care whether someone is actually 'bald' or not. |
| 8941 | We can't explain 'possibility' in terms of 'possible' worlds [Fisher] |
| Full Idea: Explaining 'it is possible that p' by saying p is true in at least one possible world doesn't get me very far. If I don't understand what possibility is, then appealing to possible worlds is not going to do me much good. | |
| From: Jennifer Fisher (On the Philosophy of Logic [2008], 06.III) | |
| A reaction: This seems so blatant that I assume friends of possible worlds will have addressed the problem. Note that you will also need to understand 'possible' to define necessity as 'true in all possible worlds'. Necessarily-p is not-possibly-not-p. |
| 8947 | If all truths are implied by a falsehood, then not-p might imply both q and not-q [Fisher] |
| Full Idea: If all truths are implied by a falsehood, then 'if there are no trees in the park then there is no shade' and 'if there are no trees in the park there is plenty of shade' both come out as true. Intuitively, though, the second one is false. | |
| From: Jennifer Fisher (On the Philosophy of Logic [2008], 08.I) | |
| A reaction: The rule that a falsehood implies all truths must be the weakest idea in classical logic, if it actually implies a contradiction. This means we must take an interest in relevance logics. |
| 8949 | In relevance logic, conditionals help information to flow from antecedent to consequent [Fisher] |
| Full Idea: A good account of relevance logic suggests that a conditional will be true when the flow of information is such that a conditional is the device that helps information to flow from the antecedent to the consequent. | |
| From: Jennifer Fisher (On the Philosophy of Logic [2008], 08.III) | |
| A reaction: Hm. 'If you are going out, you'll need an umbrella'. This passes on information about 'out', but also brings in new information. 'If you are going out, I'm leaving you'. What flows is an interpretation of the antecedent. Tricky. |
| 21103 | Moral questions can only be decided by common opinion [Hume] |
| Full Idea: Though an appeal to general opinion may justly, in the speculative sciences of metaphysics, natural philosophy or astronomy, be deemed unfair, yet in all questions with regard to morals there is really no other standard for deciding controversies. | |
| From: David Hume (Of the original contract [1741], p.291) | |
| A reaction: Surely this is too pessimistic. Common opinion decided to burn people to death for being witches. Common opinion may usually win, but there must sometimes be good grounds for resisting it. |
| 3032 | I can form no notion of what the good is [Amphis] |
| Full Idea: What the good is I no more can form a notion of, than of the good of Plato. | |
| From: Amphis (comedies (frags) [c.350 BCE]), quoted by Diogenes Laertius - Lives of Eminent Philosophers 03.1.22 | |
| A reaction: It was evidently a running joke in the ancient world that no one could define Plato's Form of the Good. He was said to have written a book on it, now lost. |
| 21099 | People must have agreed to authority, because they are naturally equal, prior to education [Hume] |
| Full Idea: When we consider how nearly equal all men are in their bodily force, and even in their mental powers and faculties, till cultivated by education, ...then nothing but their own consent could at first associate them together, and subject them to authority. | |
| From: David Hume (Of the original contract [1741], p.276) | |
| A reaction: This doesn't sound very convincing. Some people are much better suited than others to training and education. Men vary enormously in size. |
| 21100 | The idea that society rests on consent or promises undermines obedience [Hume] |
| Full Idea: Were you to preach in most parts of the world that political connections are founded altogether on voluntary consent or a mutual promise, the magistrate would soon imprison you as seditious for loosening the ties of obedience. | |
| From: David Hume (Of the original contract [1741], p.278) | |
| A reaction: He cites obedience as the prime civic virtue, because the law can't operate without it. He doesn't seem to consider the limiting cases of obedience, which makes him essentially a conservative. |
| 20495 | We no more give 'tacit assent' to the state than a passenger carried on board a ship while asleep [Hume] |
| Full Idea: [If we give 'tacit' assent to the state] ...we may as well assert that a man, by remaining in a vessel, freely consents to the dominion of the master, though he was carried aboard while asleep. | |
| From: David Hume (Of the original contract [1741], p.283) | |
| A reaction: We should probably drop the whole idea that we give assent to the state. We are stuck with a state, and a few of us can escape, if it seems important enough, but most of us have no choice. He hope to assent to the controllers of the state. |
| 21101 | The people would be amazed to learn that government arises from their consent [Hume] |
| Full Idea: When we assert that all lawful government arises from the consent of the people, we certainly do them a great deal more honour than they deserve, or even expect or desire from us. | |
| From: David Hume (Of the original contract [1741], p.285) | |
| A reaction: Hume has no interest in the purely abstract idea of a contract, and scorns Locke's idea of tacit consent to government. I assume he would dismiss Rawls as unrealistic theorising. Hume loves peace, and is alarmed by change. |
| 6703 | Poor people lack the knowledge or wealth to move to a different state [Hume] |
| Full Idea: Can we seriously say, that a poor peasant or artisan has a free choice to leave his country, when he knows no foreign language or manners, and lives, from day to day, by the small wages that he acquires? | |
| From: David Hume (Of the original contract [1741], p.283) | |
| A reaction: Of course, in the nineteenth century the Scottish poor did, going to America, which welcomed the poor, and spoke English. Hume's point is the right reply to anyone who says 'If you don't like it, go elsewhere'. Also 'No! Change it!' |
| 21102 | We all know that the history of property is founded on injustices [Hume] |
| Full Idea: Reason tells us that there is no property in durable objects, such as land or houses, when carefully examined in passing from hand to hand, but must, in some period, have been founded on fraud and injustice. | |
| From: David Hume (Of the original contract [1741], p.288) | |
| A reaction: A prime objection to Nozick, who fantasises about an initial position of just ownership, which can then be the subject of just contracts. In 1866 thousands of white people were granted land in the USA, but not a single black freed slave got anything. |