26 ideas
| 10041 | Impredicative Definitions refer to the totality to which the object itself belongs [Gödel] |
| Full Idea: Impredicative Definitions are definitions of an object by reference to the totality to which the object itself (and perhaps also things definable only in terms of that object) belong. | |
| From: Kurt Gödel (Russell's Mathematical Logic [1944], n 13) |
| 17884 | Mathematical set theory has many plausible stopping points, such as finitism, and predicativism [Koellner] |
| Full Idea: There are many coherent stopping points in the hierarchy of increasingly strong mathematical systems, starting with strict finitism, and moving up through predicativism to the higher reaches of set theory. | |
| From: Peter Koellner (On the Question of Absolute Undecidability [2006], Intro) |
| 17893 | 'Reflection principles' say the whole truth about sets can't be captured [Koellner] |
| Full Idea: Roughly speaking, 'reflection principles' assert that anything true in V [the set hierarchy] falls short of characterising V in that it is true within some earlier level. | |
| From: Peter Koellner (On the Question of Absolute Undecidability [2006], 2.1) |
| 21716 | In simple type theory the axiom of Separation is better than Reducibility [Gödel, by Linsky,B] |
| Full Idea: In the superior realist and simple theory of types, the place of the axiom of reducibility is not taken by the axiom of classes, Zermelo's Aussonderungsaxiom. | |
| From: report of Kurt Gödel (Russell's Mathematical Logic [1944], p.140-1) by Bernard Linsky - Russell's Metaphysical Logic 6.1 n3 | |
| A reaction: This is Zermelo's Axiom of Separation, but that too is not an axiom of standard ZFC. |
| 10035 | Mathematical Logic is a non-numerical branch of mathematics, and the supreme science [Gödel] |
| Full Idea: 'Mathematical Logic' is a precise and complete formulation of formal logic, and is both a section of mathematics covering classes, relations, symbols etc, and also a science prior to all others, with ideas and principles underlying all sciences. | |
| From: Kurt Gödel (Russell's Mathematical Logic [1944], p.447) | |
| A reaction: He cites Leibniz as the ancestor. In this database it is referred to as 'theory of logic', as 'mathematical' seems to be simply misleading. The principles of the subject are standardly applied to mathematical themes. |
| 10042 | Reference to a totality need not refer to a conjunction of all its elements [Gödel] |
| Full Idea: One may, on good grounds, deny that reference to a totality necessarily implies reference to all single elements of it or, in other words, that 'all' means the same as an infinite logical conjunction. | |
| From: Kurt Gödel (Russell's Mathematical Logic [1944], p.455) |
| 17894 | We have no argument to show a statement is absolutely undecidable [Koellner] |
| Full Idea: There is at present no solid argument to the effect that a given statement is absolutely undecidable. | |
| From: Peter Koellner (On the Question of Absolute Undecidability [2006], 5.3) |
| 10038 | A logical system needs a syntactical survey of all possible expressions [Gödel] |
| Full Idea: In order to be sure that new expression can be translated into expressions not containing them, it is necessary to have a survey of all possible expressions, and this can be furnished only by syntactical considerations. | |
| From: Kurt Gödel (Russell's Mathematical Logic [1944], p.448) | |
| A reaction: [compressed] |
| 10046 | The generalized Continuum Hypothesis asserts a discontinuity in cardinal numbers [Gödel] |
| Full Idea: The generalized Continuum Hypothesis says that there exists no cardinal number between the power of any arbitrary set and the power of the set of its subsets. | |
| From: Kurt Gödel (Russell's Mathematical Logic [1944], p.464) |
| 17890 | There are at least eleven types of large cardinal, of increasing logical strength [Koellner] |
| Full Idea: Some of the standard large cardinals (in order of increasing (logical) strength) are: inaccessible, Mahlo, weakly compact, indescribable, Erdös, measurable, strong, Wodin, supercompact, huge etc. (...and ineffable). | |
| From: Peter Koellner (On the Question of Absolute Undecidability [2006], 1.4) | |
| A reaction: [I don't understand how cardinals can have 'logical strength', but I pass it on anyway] |
| 17887 | PA is consistent as far as we can accept, and we expand axioms to overcome limitations [Koellner] |
| Full Idea: To the extent that we are justified in accepting Peano Arithmetic we are justified in accepting its consistency, and so we know how to expand the axiom system so as to overcome the limitation [of Gödel's Second Theorem]. | |
| From: Peter Koellner (On the Question of Absolute Undecidability [2006], 1.1) | |
| A reaction: Each expansion brings a limitation, but then you can expand again. |
| 10039 | Some arithmetical problems require assumptions which transcend arithmetic [Gödel] |
| Full Idea: It has turned out that the solution of certain arithmetical problems requires the use of assumptions essentially transcending arithmetic. | |
| From: Kurt Gödel (Russell's Mathematical Logic [1944], p.449) | |
| A reaction: A nice statement of the famous result, from the great man himself, in the plainest possible English. |
| 17891 | Arithmetical undecidability is always settled at the next stage up [Koellner] |
| Full Idea: The arithmetical instances of undecidability that arise at one stage of the hierarchy are settled at the next. | |
| From: Peter Koellner (On the Question of Absolute Undecidability [2006], 1.4) |
| 10043 | Mathematical objects are as essential as physical objects are for perception [Gödel] |
| Full Idea: Classes and concepts may be conceived of as real objects, ..and are as necessary to obtain a satisfactory system of mathematics as physical bodies are necessary for a satisfactory theory of our sense perceptions, with neither case being about 'data'. | |
| From: Kurt Gödel (Russell's Mathematical Logic [1944], p.456) | |
| A reaction: Note that while he thinks real objects are essential for mathematics, be may not be claiming the same thing for our knowledge of logic. If logic contains no objects, then how could mathematics be reduced to it, as in logicism? |
| 10045 | Impredicative definitions are admitted into ordinary mathematics [Gödel] |
| Full Idea: Impredicative definitions are admitted into ordinary mathematics. | |
| From: Kurt Gödel (Russell's Mathematical Logic [1944], p.464) | |
| A reaction: The issue is at what point in building an account of the foundations of mathematics (if there be such, see Putnam) these impure definitions should be ruled out. |
| 23814 | Every human yearns for an unattainable transcendent good [Weil] |
| Full Idea: There is a reality outside the world …outside any sphere that is accessible to human faculties. Corresponding to this reality, at the centre of the human heart, is the longing for an absolute good, which is always there and never appeased by this world. | |
| From: Simone Weil (Draft Statement of Human Obligations [1943], p.221) | |
| A reaction: I don't believe in any sort of transcendent reality, but I can identify with this. Even if you have a highly naturalistic view of what is valuable (see late Philippa Foot), there is this indeterminate yearning for that value. |
| 23824 | Where human needs are satisfied we find happiness, friendship and beauty [Weil] |
| Full Idea: Any place where the needs of human beings are satisfied can be recognised by the fact that there is a flowering of fraternity, joy, beauty, and happiness. | |
| From: Simone Weil (Draft Statement of Human Obligations [1943], p.230) | |
| A reaction: Weil writes a lengthy analysis of what she sees as the basic human needs, beyond the obvious food, water etc. An excellent place to start a line of political thought. |
| 23815 | We cannot equally respect what is unequal, so equal respect needs a shared ground [Weil] |
| Full Idea: It is impossible to feel equal respect for things that are in fact unequal unless the respect is given to something that is identical in all of them. Men are all unequal in all their relations with things of this world. | |
| From: Simone Weil (Draft Statement of Human Obligations [1943], p.223) | |
| A reaction: Weil votes for some link to transcendence in each of us, but I would prefer some more naturalistic proposal for what we all have in common. There are plenty of aspects which unite all human beings, which grounds this unconditional respect. |
| 23823 | Life needs risks to avoid sickly boredom [Weil] |
| Full Idea: The boredom produced by a complete absence of risk is a sickness of the human soul. | |
| From: Simone Weil (Draft Statement of Human Obligations [1943], p.229) | |
| A reaction: An unusual analysis of boredom. I think it is probably purposeful activity that we need, rather than actual risk, with all the stresses that involves. Risks are justified by their rewards. |
| 23822 | We all need to partipate in public tasks, and take some initiative [Weil] |
| Full Idea: The human soul has need of disciplined participation in a common task of public value, and it has need of personal initiative within this participation. | |
| From: Simone Weil (Draft Statement of Human Obligations [1943], p.229) | |
| A reaction: The intrusion of competitive capitalism into almost every area of modern life has more or less eliminated such activities. Only state employees now have such satisfactions, on the whole. I admire Weil's approach here. |
| 23817 | We need both equality (to attend to human needs) and hierarchy (as a scale of responsibilities) [Weil] |
| Full Idea: The human soul has need of equality and of hierarchy. Equality is the public recognition …of the principal that an equal degree of attention is due to the needs of all human beings. Hierarchy is the scale of responsibilities. | |
| From: Simone Weil (Draft Statement of Human Obligations [1943], p.228) | |
| A reaction: This is the conservative aspect of Weil's largely radical political thinking. Presumably what we respect in these people is their responsibilies, and not their mere rank. Idle members of the British House of Lords have no rank in this hierarchy. |
| 23819 | Deliberate public lying should be punished [Weil] |
| Full Idea: Every avoidable material falsehood publicly asserted should become a punishable offence. | |
| From: Simone Weil (Draft Statement of Human Obligations [1943], p.228) | |
| A reaction: Yes please! The early 21st century has become the time when truth lost all value in public life. Lying to the House of Commons in the UK required instant resignation 50 years ago. Now it is just a source of laughter. No freedom to lie! |
| 23818 | We have liberty in the space between nature and accepted authority [Weil] |
| Full Idea: Liberty is the power of choice within the latitude left between the direct constraint of natural forces and the authority accepted as legitimate. | |
| From: Simone Weil (Draft Statement of Human Obligations [1943], p.228) | |
| A reaction: Accepting legitimate authority is a nicely softened version of the social contract. We often find that the office and rank are accepted as legitimate, but then are unable to accept the appalling individual who holds the office. |
| 23820 | People need personal and collective property, and a social class lacking property is shameful [Weil] |
| Full Idea: The human soul has need of both personal property and collective property. …The existence of a social class defined by the lack of personal and collective property is as shameful as slavery. | |
| From: Simone Weil (Draft Statement of Human Obligations [1943], p.229) | |
| A reaction: Nice. Particularly the idea that we all need collective property, such as parks and beaches and public buildings. |
| 23821 | Crime should be punished, to bring the perpetrator freely back to morality [Weil] |
| Full Idea: The human soul needs punishment and honour. A committer of crime has become exiled from good, and needs to be reintegrated with it through suffering. This aims to bring the soul to recognise freely some day that is infliction was just. | |
| From: Simone Weil (Draft Statement of Human Obligations [1943], p.229) | |
| A reaction: The Scanlon contractualist approach to punishment - that the victim of it accepts its justice. Given her saintly character, Simone had a very tough view of this issue. |
| 23816 | Attention to a transcendent reality motivates a duty to foster the good of humanity [Weil] |
| Full Idea: Anyone whose attention and love are directed towards the reality outside the world recognises that he is bound by the permanent obligation to remedy …all the privations of soul and body which are liable to destroy or damage any human being whatsoever. | |
| From: Simone Weil (Draft Statement of Human Obligations [1943], p.225) | |
| A reaction: [abridged] An interesting attempt to articulate the religious motivation of morality. The Euthyphro question remains - of why this vision of a wholly good higher morality should motivate anyone, unless they already possess a desire for that good. |