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. |
| 10800 | The values of variables can't determine existence, because they are just expressions [Ryle, by Quine] |
| Full Idea: Ryle objected somewhere to my dictum that 'to be is to be the value of a variable', arguing that the values of variables are expressions, and hence that my dictum repudiates all things except expressions. | |
| From: report of Gilbert Ryle (works [1950]) by Willard Quine - Reply to Professor Marcus p.183 | |
| A reaction: I have a lot of sympathy with Ryle's view, and I associate it with the peculiar Millian view that we can somehow replace a name in a sentence with the actual physical object. Objects can't be parts of sentences - and maybe they can't be 'values'. |
| 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. |
| 7404 | Nations are not obliged to help one-another, but are obliged not to harm one another [Grotius, by Tuck] |
| Full Idea: Grotius explored the implications of the idea that nation-states were under no obligation to help one another, but they were obliged not to harm each other. | |
| From: report of Hugo Grotius (On the Law of War and Peace [1625]) by Richard Tuck - Hobbes Ch.1 | |
| A reaction: This is quite a striking disanalogy between accepted personal morality and political morality. There are signs in recent years of some recognition that other nations should not just sit and watch suffering. |
| 7402 | Everyone has a right of self-preservation, and harming others is usually unjustifiable [Grotius, by Tuck] |
| Full Idea: Grotius said that all men would agree that everyone has a fundamental right to preserve themselves, and that wanton or unnecessary injury to another person is unjustifiable. | |
| From: report of Hugo Grotius (On the Law of War and Peace [1625]) by Richard Tuck - Hobbes Ch.1 | |
| A reaction: Who cares if it is 'justifiable'? Do I have to 'justify' killing a mosquito if it lands on my arm? Grotius is taking a step beyond saying that people should defend themselves, to say that they have a 'right' to - the only truly basic right. |
| 21938 | Democracy needs respect for individuality, but the 'community of friends' implies strict equality [Grotius] |
| Full Idea: There is no democracy without respect for irreducible singularity, but there is no democracy with the 'community of friends' without the calculation of majorities, without identifiable representable subjects, all equal. | |
| From: Hugo Grotius (On the Law of War and Peace [1625]), quoted by Simon Glendinning - Derrida: A Very Short Introduction 7 | |
| A reaction: [source not given] Derrida calls this conflict 'tragic'. The obvious reply is that equality is not an absolute. We can be equal in voting rights while being unequal in height or musical talent. |
| 19845 | A person is free to renounce their state, as long as it is not a moment of crisis [Grotius, by Rousseau] |
| Full Idea: Grotius thinks that each person can renounce his state and leave the country. (n15: provided it is not to evade one's duty the moment the homeland needs us; this would be criminal and punishable; it would not be withdrawal, but desertion) | |
| From: report of Hugo Grotius (On the Law of War and Peace [1625]) by Jean-Jacques Rousseau - The Social Contract (tr Cress) III.18 | |
| A reaction: The obvious example is Britons going to America in 1939, or (more controversially) conscripts going to Canada to avoid fighting in Vietnam. I'm unclear whether the idea in the note is that of Grotius or of Rousseau). Is tax exile OK, then? |
| 22133 | Grotius and Pufendorf based natural law on real (rather than idealised) humanity [Grotius, by Ford,JD] |
| Full Idea: Grotius and Pufendorf transformed the natural law tradition by starting from identifiable traits of human nature rather than ideas about what human beings ought to be. | |
| From: report of Hugo Grotius (On the Law of War and Peace [1625]) by J.D. Ford - Pufendorf, Samuel p.863 |
| 7406 | A natural right of self-preservation is balanced by a natural law to avoid unnecessary harm [Grotius, by Tuck] |
| Full Idea: For Grotius, there was a fundamental 'natural right' of self-preservation upon which all known moralities and codes of social behaviour must have been constructed, but it is balanced by a fundament duty or 'natural law' to abstain from harming others. | |
| From: report of Hugo Grotius (On the Law of War and Peace [1625]) by Richard Tuck - Hobbes Ch.2 | |
| A reaction: This theory has the virtue of economy, but I don't see how you can clearly justify those particular natural rights and laws, without allowing others to creep in, such as a right to a decent share of food, or a law requiring some fairness. |
| 7403 | Grotius ignored elaborate natural law theories, preferring a basic right of self-preservation [Grotius, by Tuck] |
| Full Idea: Grotius said there was a minimum core of morality (based on self-preservation), and disregarded the elaborate accounts of principles of natural law which Aristotelians had always sought to develop. | |
| From: report of Hugo Grotius (On the Law of War and Peace [1625]) by Richard Tuck - Hobbes Ch.1 | |
| A reaction: Aquinas would be the key Aristotelian here. I tend towards the Aristotelian view. If you go for the minimal view, it is not clear why there is a 'right' to self-preservation, rather than a mere desire for it. |
| 23585 | It is permissible in a just cause to capture a place in neutral territory [Grotius] |
| Full Idea: It is permissible for one who is waging a just war to take possession of a place situated in a country free from hostilities. | |
| From: Hugo Grotius (On the Law of War and Peace [1625], II.ii.x), quoted by Michael Walzer - Just and Unjust Wars 15 n | |
| A reaction: This rejects Combatant Equality, allowing the just to do what is morally forbidden to the unjust. |
| 6892 | Moral principles have some validity without a God commanding obedience [Grotius, by Mautner] |
| Full Idea: In the Prolegomena to his work there is a famous statement that moral principles laid down in the work would have some degree of validity even if there was no God commanding obedience. | |
| From: report of Hugo Grotius (On the Law of War and Peace [1625]) by Thomas Mautner - Penguin Dictionary of Philosophy p.229 | |
| A reaction: I am not clear why Grotius felt obliged to qualify his claim with the phrase 'some degree'. I don't see how God's command can affect the 'validity' of morality, or how there can be a middle ground between dependence on and independence of God. |