20 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. |
| 9261 | The 'Ethics' is disappointing, because it fails to try to justify our duties [Prichard] |
| Full Idea: Reading the 'Ethics' is so disappointing, because Aristotle does not try to convince us that we really ought to do what our non-reflective consciousness has hitherto believed we ought to do. | |
| From: H.A. Prichard (Does moral phil rest on a mistake? [1912]) | |
| A reaction: Aristotle didn't speak the language of 'duty' (see Idea 2172), but he could work it into his account if Prichard asked nicely. I take the truly virtuous person to be, above all, a wonderful citizen. Duties are contractual; good deeds flow from virtue. |
| 9262 | The mistake is to think we can prove what can only be seen directly in moral thinking [Prichard] |
| Full Idea: Moral Philosophy rests on the mistake of supposing the possibility of proving what can only be apprehended directly by an act of moral thinking. | |
| From: H.A. Prichard (Does moral phil rest on a mistake? [1912]) | |
| A reaction: This is a beginning of the rebellion against the Enlightenment Project in ethics, which is why Prichard has become popular. At bottom he is offering intuition ('direct moral thinking'), which is a frustratingly thin concept. |
| 9260 | Virtues won't generate an obligation, so it isn't a basis for morality [Prichard] |
| Full Idea: It is untrue to urge that, since courage is a virtue, we ought to act courageously. We feel an obligation to act, but not from a certain desire. The action is done from obligation, so isn't an act of courage. ..In fact, virtue is no basis for morality. | |
| From: H.A. Prichard (Does moral phil rest on a mistake? [1912]) | |
| A reaction: One of the few interesting and direct attacks on virtue theory, before its modern revival. Prichard urges a perception of what is valuable (or good) as the basis for obligation and right action. He is right that values come first, in virtue and elsewhere. |
| 9259 | We feel obligations to overcome our own failings, and these are not relations to other people [Prichard] |
| Full Idea: The relation involved in an obligation need not be a relation to another at all. Thus we should admit that there is an obligation to overcome our natural timidity or greediness, and this involves no relations to others. | |
| From: H.A. Prichard (Does moral phil rest on a mistake? [1912]) | |
| A reaction: An interesting un-Aristotelian and individualistic view of virtue. Why would we want to rid ourselves of timidity or greediness? Either it is self-interested, or we wish to be better citizens. See Richard Taylor on duty. |
| 9258 | If pain were instrinsically wrong, it would be immoral to inflict it on ourselves [Prichard] |
| Full Idea: If the badness of pain were the reason why we ought not to inflict pain on another, it would equally be a reason why we ought not to inflict pain on ourselves; yet, though we would call such behaviour foolish, we wouldn't think it wrong. | |
| From: H.A. Prichard (Does moral phil rest on a mistake? [1912], n4) | |
| A reaction: A very nice point. Note that it will equally well apply to 'benefit' or 'preferences', or any other ideal which utilitarians set out to maximise. It may not be bad to hurt yourself, but it might still be bad to harm yourself. |
| 21275 | Unlike a stone, the parts of a watch are obviously assembled in order to show the time [Paley] |
| Full Idea: When we come to inspect a watch we perceive (what we could not discover in a stone) that its several parts are put together for a purpose, to produce motion, and that motion so regulated as to point out the hour of the day. | |
| From: William Paley (Natural Theology [1802], Ch 1) | |
| A reaction: Microscopic examination of the stone would have surprised Paley. Should we infer a geometer because the sun is spherical? Crytals look designed, but are explained by deeper chemistry. |
| 21276 | From the obvious purpose and structure of a watch we must infer that it was designed [Paley] |
| Full Idea: The inference is inevitable that the watch had a maker; that there must have existed, at some time, an artificer or artificers who formed it for the purpose which we find it actually to answer, who designed its use. | |
| From: William Paley (Natural Theology [1802], Ch 1) | |
| A reaction: It rather begs the question to refer to an ordered structure as a 'design'. Why do we think it is absurd to think the the 'purpose' of the sun is to benefit mankind? Suppose we found a freakish natural sundial in the woods. |
| 21277 | Even an imperfect machine can exhibit obvious design [Paley] |
| Full Idea: It is not necessary that a machine be perfect, in order to show with what design it was made. | |
| From: William Paley (Natural Theology [1802], Ch 1) | |
| A reaction: This encounters Hume's point that you will then have to infer that the designer contains similar imperfections. If you look at plagues, famines and mothers dying in childbirth (see Mill), you might wish the designer had never started. |
| 21278 | All the signs of design found in a watch are also found in nature [Paley] |
| Full Idea: Every indication of contrivance, every manifestation of design, which existed in the watch, exists in the works of nature. | |
| From: William Paley (Natural Theology [1802], Ch.3) | |
| A reaction: This is far from obvious. It was crucial to the watch analogy that we immediately see its one self-evident purpose. No one looks at nature and says 'Aha, I know what this is all for'. |
| 21357 | No organ shows purpose more obviously than the eyelid [Paley] |
| Full Idea: The eyelid defends the eye; it wipes it; it closes it in sleep. Are there, in any work of art whatever, purposes more evident than those which this organ fulfils? | |
| From: William Paley (Natural Theology [1802], p.24), quoted by Armand Marie LeRoi - The Lagoon: how Aristotle invented science 031 | |
| A reaction: Nice to have another example, in addition to the watch. He is not wholly wrong, because it is impossible to give an evolutionary account of the development of the eyelid without referring to some sort of teleological aspect. The eyelid has a function. |