19 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! |
| 22462 | We should speak the truth, but also preserve and pursue it [Foot] |
| Full Idea: There belongs to truthfulness not only the avoidance of lying but also that other kind of attachment to truth which has to do with its preservation and pursuit. | |
| From: Philippa Foot (Utilitarianism and the Virtues [1985], p.74) | |
| A reaction: This is truth as a value, rather than as a mere phenomenon of accurate thought and speech. The importance of 'preserving' the truth is the less common part of this idea. |
| 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. |
| 17744 | De Morgan started the study of relations and their properties [De Morgan, by Walicki] |
| Full Idea: De Morgan started the sustained interest in the study of relations and their properties. | |
| From: report of Augustus De Morgan (On the Syllogism IV [1859]) by Michal Walicki - Introduction to Mathematical Logic History D.1.1 |
| 13501 | De Morgan found inferences involving relations, which eluded Aristotle's syllogistic [De Morgan, by Hart,WD] |
| Full Idea: There was a prejudice against relations (in favour of properties) but De Morgan and others that impeccable inferences turn on relations and elude Aristotle's syllogistic. Thus: All horses are animals. Hence, all heads of horses are heads of animals. | |
| From: report of Augustus De Morgan (On the Syllogism IV [1859]) by William D. Hart - The Evolution of Logic 4 | |
| A reaction: This is actually an early example of modern analytic philosophy in action. You start with the inferences, and then work back to the ontology and the definition of concepts. But in pinning down such concepts, do we miss their full meaning? |
| 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. |
| 22458 | Consequentialists can hurt the innocent in order to prevent further wickedness [Foot] |
| Full Idea: For consequentialists there will be nothing that it will not be right to do to a perfectly innocent individual, if that is the only way of preventing another agent from doing more things of the same kind. | |
| From: Philippa Foot (Utilitarianism and the Virtues [1985], p.61) | |
| A reaction: This is her generalised version that Williams dramatised as Jim and the Indians. Roughly, if you achieve a good outcome, it matters little how it is achieved. Foot sees consequentialism as the main problem with utilitarianism. |
| 22460 | Why might we think that a state of affairs can be morally good or bad? [Foot] |
| Full Idea: We should ask why we think that it makes sense to talk about morally good and bad states of affairs. | |
| From: Philippa Foot (Utilitarianism and the Virtues [1985], p.68) | |
| A reaction: This is the key question in her attack on consequentialism. There is nothing 'morally' good about my football team winning a great victory. |
| 22461 | Good outcomes are not external guides to morality, but a part of virtuous actions [Foot] |
| Full Idea: It is not that maximum welfare or 'the best outcome' stands outside morality as it foundation and arbiter, but rather that it appears within morality as the end of one of the virtues. | |
| From: Philippa Foot (Utilitarianism and the Virtues [1985], p.73) | |
| A reaction: She cites justice and benevolence as aiming at different (and even conflicting) outcomes. I'm not sure about her distinction between 'outside' and 'within' morality. I suppose a virtuously created end is a moral end, unlike mere good states of affairs. |
| 22464 | The idea of a good state of affairs has no role in the thought of Aristotle, Rawls or Scanlon [Foot] |
| Full Idea: The idea of the goodness of total states of affairs played no part in Aristotle's moral philosophy, and in modern times plays not part either in Rawls's account of justice or in the theories of more thoroughgoing contractualists such as Scanlon. | |
| From: Philippa Foot (Utilitarianism and the Virtues [1985], p.76) | |
| A reaction: We can add Kant to that. But if the supremely good state of affairs were permanently achieved, would that make morality irrelevant? A community of the exceptionally virtuous would not need the veil of ignorance, or contracts. |
| 22463 | Morality is seen as tacit legislation by the community [Foot] |
| Full Idea: Morality is thought of as a kind of tacit legislation by the community. | |
| From: Philippa Foot (Utilitarianism and the Virtues [1985], p.75) | |
| A reaction: Foot presents this as a utilitarian doctrine, because the tacit legislation is felt to produce the best outcomes. This is Nietzsche's good and evil, beyond which he wished to go (presumably following other values). |
| 22459 | For consequentialism, it is irrational to follow a rule which in this instance ends badly [Foot] |
| Full Idea: It would be irrational to obey even the most useful rule if in a particular instance we clearly see that such obedience will not have the best results. | |
| From: Philippa Foot (Utilitarianism and the Virtues [1985], p.62) | |
| A reaction: This is the simple reason why attempts at rule utilitarianism always lead back to act utilitarianism. Another way of putting it is that a good rule can only be assessed by the outcomes of individual acts that follow it. |