26 ideas
| 21704 | 'Impredictative' definitions fix a class in terms of the greater class to which it belongs [Linsky,B] |
| Full Idea: The ban on 'impredicative' definitions says you can't define a class in terms of a totality to which that class must be seen as belonging. | |
| From: Bernard Linsky (Russell's Metaphysical Logic [1999], 1) | |
| A reaction: So that would be defining 'citizen' in terms of the community to which the citizen belongs? If you are asked to define 'community' and 'citizen' together, where do you start? But how else can it be done? Russell's Reducibility aimed to block this. |
| 21705 | Reducibility says any impredicative function has an appropriate predicative replacement [Linsky,B] |
| Full Idea: The Axiom of Reducibility avoids impredicativity, by asserting that for any predicate of given arguments defined by quantifying over higher-order functions or classes, there is another co-extensive but predicative function of the same type of arguments. | |
| From: Bernard Linsky (Russell's Metaphysical Logic [1999], 1) | |
| A reaction: Eventually the axiom seemed too arbitrary, and was dropped. Linsky's book explores it. |
| 21727 | Definite descriptions theory eliminates the King of France, but not the Queen of England [Linsky,B] |
| Full Idea: The theory of definite descriptions may eliminate apparent commitment to such entities as the present King of France, but certainly not to the present Queen of England. | |
| From: Bernard Linsky (Russell's Metaphysical Logic [1999], 7.3) |
| 21719 | Extensionalism means what is true of a function is true of coextensive functions [Linsky,B] |
| Full Idea: With the principle of extensionality anything true of one propositional functions will be true of every coextensive one. | |
| From: Bernard Linsky (Russell's Metaphysical Logic [1999], 6.3) |
| 21723 | The task of logicism was to define by logic the concepts 'number', 'successor' and '0' [Linsky,B] |
| Full Idea: The problem for logicism was to find definitions of the primitive notions of Peano's theory, number, successor and 0, in terms of logical notions, so that the postulates could then be derived by logic alone. | |
| From: Bernard Linsky (Russell's Metaphysical Logic [1999], 7) | |
| A reaction: Both Frege and Russell defined numbers as equivalence classes. Successor is easily defined (in various ways) in set theory. An impossible set can exemplify zero. The trouble for logicism is this all relies on sets. |
| 21721 | Higher types are needed to distinguished intensional phenomena which are coextensive [Linsky,B] |
| Full Idea: The higher types are needed for intensional phenomena, cases where the same class is picked out by distinct propositional functions. | |
| From: Bernard Linsky (Russell's Metaphysical Logic [1999], 6.4) | |
| A reaction: I take it that in this way 'x is renate' can be distinguished from 'x is cordate', a task nowadays performed by possible worlds. |
| 21703 | Types are 'ramified' when there are further differences between the type of quantifier and its range [Linsky,B] |
| Full Idea: The types is 'ramified' because there are further differences between the type of a function defined in terms of a quantifier ranging over other functions and the type of those other functions, despite the functions applying to the same simple type. | |
| From: Bernard Linsky (Russell's Metaphysical Logic [1999], 1) | |
| A reaction: Not sure I understand this, but it evidently created difficulties for dealing with actual mathematics, and Ramsey showed how you could manage without the ramifications. |
| 21714 | The ramified theory subdivides each type, according to the range of the variables [Linsky,B] |
| Full Idea: The original ramified theory of types ...furthern subdivides each of the types of the 'simple' theory according to the range of the bound variables used in the definition of each propositional function. | |
| From: Bernard Linsky (Russell's Metaphysical Logic [1999], 6) | |
| A reaction: For a non-intiate like me it certainly sounds disappointing that such a bold and neat theory because a tangle of complications. Ramsey and Russell in the 1920s seem to have dropped the ramifications. |
| 21713 | Did logicism fail, when Russell added three nonlogical axioms, to save mathematics? [Linsky,B] |
| Full Idea: It is often thought that Logicism was a failure, because after Frege's contradiction, Russell required obviously nonlogical principles, in order to develop mathematics. The axioms of Reducibility, Infinity and Choice are cited. | |
| From: Bernard Linsky (Russell's Metaphysical Logic [1999], 6) | |
| A reaction: Infinity and Choice remain as axioms of the standard ZFC system of set theory, which is why set theory is always assumed to be 'up to its neck' in ontological commitments. Linsky argues that Russell saw ontology in logic. |
| 21715 | For those who abandon logicism, standard set theory is a rival option [Linsky,B] |
| Full Idea: ZF set theory is seen as a rival to logicism as a foundational scheme. Set theory is for those who have given up the project of reducing mathematics to logic. | |
| From: Bernard Linsky (Russell's Metaphysical Logic [1999], 6.1) | |
| A reaction: Presumably there are other rivals. Set theory has lots of ontological commitments. One could start at the other end, and investigate the basic ontological commitments of arithmetic. I have no idea what those might be. |
| 21729 | Construct properties as sets of objects, or say an object must be in the set to have the property [Linsky,B] |
| Full Idea: Rather than directly constructing properties as sets of objects and proving neat facts about properties by proxy, we can assert biconditionals, such as that an object has a property if and only if it is in a certain set. | |
| From: Bernard Linsky (Russell's Metaphysical Logic [1999], 7.6) | |
| A reaction: Linsky is describing Russell's method of logical construction. I'm not clear what is gained by this move, but at least it is a variant of the usual irritating expression of properties as sets of objects. |
| 22167 | Our images of bodies are not produced by the bodies, but by our own minds [Augustine, by Aquinas] |
| Full Idea: Augustine says bodies don't form images in our spirit; our spirit does that itself with amazing quickness. ...So the appearances under which mind knows things aren't drawn from the things themselves. | |
| From: report of Augustine (works [c.415]) by Thomas Aquinas - Quodlibeta 8.2.1 | |
| A reaction: This is Augustine's theory of 'illumination' - that God creates experience within us. His theory was soon discarded by the early scholastics. |
| 22117 | Our minds grasp reality by direct illumination (rather than abstraction from experience) [Augustine, by Matthews] |
| Full Idea: Instead of supposing that what we know can be abstracted from sensible particulars that instantiate such knowledge, Augustine insists that our mind is so constituted as to see 'intelligible realities' directly by inner illumination. | |
| From: report of Augustine (works [c.415]) by Gareth B. Matthews - Augustine p.74 | |
| A reaction: His 'theory of illumination'. This seems to be a sort of super-rationalism. This doesn't make clear the role of sensations. Surely he doesn't thing that we just bypass them? |
| 22118 | Augustine created the modern concept of the will [Augustine, by Matthews] |
| Full Idea: The modern concept of the will is often said to originate with Augustine. | |
| From: report of Augustine (works [c.415]) by Gareth B. Matthews - Augustine p.74 | |
| A reaction: I'm beginning to think that this is the source of the trouble. How can a thing be intrinsically free? Surely freedom is always a contextual concept? |
| 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. |
| 4348 | Love, and do what you will [Augustine] |
| Full Idea: Love, and do what you will. | |
| From: Augustine (works [c.415]) | |
| A reaction: This sounds libertarian, but Augustine had a stern concept of what love required. It nicely captures one of the essential ideas of virtue ethics. |
| 7821 | Pagans produced three hundred definitions of the highest good [Augustine, by Grayling] |
| Full Idea: Augustine claimed that the pagan schools between them had produced nearly three hundred different definitions of the highest good. | |
| From: report of Augustine (works [c.415]) by A.C. Grayling - What is Good? Ch.5 | |
| A reaction: I would expect the right definition to be in there somewhere, but no doubt Augustine's definition made it 301. Perhaps the biggest problem of human life is that (as with the Kennedy assassination) proliferating stories obscure the true story. |
| 22119 | Augustine said (unusually) that 'ought' does not imply 'can' [Augustine, by Matthews] |
| Full Idea: Augustine insisted that 'ought' does not, in any straightforward way, imply 'can' - which distinguishes him from most modern ethicists. | |
| From: report of Augustine (works [c.415]) by Gareth B. Matthews - Augustine p.74 | |
| A reaction: Not unreasonable. I ought to help my ailing friend who lives abroad, but I haven't the time or money to do it. We can experience impossibilities as duties. Impossibilities are just excuses. Augustine is opposing the Pelagian heresy. |
| 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. |
| 22116 | Augustine identified Donatism, Pelagianism and Manicheism as the main heresies [Augustine, by Matthews] |
| Full Idea: Augustine did the most to define Christian heresy. The three most prominent were Donatism, Pelagianism (that humans are perfectible), and Manicheism (that good and evil are equally basic metaphysical realities). | |
| From: report of Augustine (works [c.415]) by Gareth B. Matthews - Augustine p.73 | |
| A reaction: Manicheans had presumably been studying Empedocles. (I suppose it's too late to identify Christianity as a heresy?). |
| 19338 | Augustine said evil does not really exist, and evil is a limitation in goodness [Augustine, by Perkins] |
| Full Idea: Augustine solution to the problem of evil was to say that, strictly speaking, evil does not exist. Human beings are not part evil and part good, but rather just a limited amount of goodness. | |
| From: report of Augustine (works [c.415]) by Franklin Perkins - Leibniz: Guide for the Perplexed 2.III | |
| A reaction: Augustine was rebelling against Manicheanism, which he espoused when young, which proposed a good and an evil force. An apathetic slob seems devoid of goodness, but is not evil. It takes extra effort to perform active evil. |