13 ideas
| 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) |
| 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) |
| 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. |
| 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) |
| 23111 | If we say that freedom depends on rationality, the irrational actions are not free [Sidgwick] |
| Full Idea: If we say that a man is a free agent in proportion as he acts rationally, we cannot also say that it is by free choice that he acts irrationally. | |
| From: Henry Sidgwick (The Methods of Ethics (7th edn) [1874], p.511), quoted by John Kekes - Against Liberalism 7.4 | |
| A reaction: A very nice riposte. Clearly people can rationally choose to act irrationally, e.g. at a wild party. |
| 22371 | Determinism threatens free will if actions can be causally traced to external factors [Foot] |
| Full Idea: The determinism which worries the defender of free will is that if human action is subject to a universal law of causation, there will be for any action a set of sufficient conditions which can be traced back to factors outside the control of the agent. | |
| From: Philippa Foot (Free Will as Involving Determinism [1957], p.63) | |
| A reaction: She draws on Russell for this, but neither of them mention whether the causation is physical. Free will seems to imply non-physical causation. |
| 22372 | Not all actions need motives, but it is irrational to perform troublesome actions with no motive [Foot] |
| Full Idea: We do not expect that everything a rational man does should be done with a motive, ...but we do expect a man to have a motive for many things that he does, and would count anyone who constantly performed troublesome actions without a motive as irrational. | |
| From: Philippa Foot (Free Will as Involving Determinism [1957], p.66) | |
| A reaction: Interestng, because the assessment of whether someone is 'rational' therefore needs a criterion for when a motive seems required and when not. 'Significant' actions need a motive? |
| 23059 | Self-interest is not rational, if the self is just a succession of memories and behaviour [Sidgwick, by Gray] |
| Full Idea: Sidgwick said self-interest is not self-evidently rational. Unless we invoke a religious idea of the soul, human personality is no more than a succession of continuities in memory and behaviour. In that case, why should anyone favour their future self? | |
| From: report of Henry Sidgwick (The Methods of Ethics (7th edn) [1874]) by John Gray - Seven Types of Atheism 2 | |
| A reaction: This sounds like Locke's account of the self, as psychological continuity. We can say that our continuous self is a fiction, the hero of our own narrative. Personally I think of the self as a sustained set of brains structures which change very little. |
| 22373 | People can act out of vanity without being vain, or even vain about this kind of thing [Foot] |
| Full Idea: It makes sense to say that a man acts out of vanity on a particular occasion although he is not in general vain, or even vain about this kind of thing. | |
| From: Philippa Foot (Free Will as Involving Determinism [1957], p.69) | |
| A reaction: Aristotle tells us that virtues and vices are habits, and also have an intellectual component, implying that the person believes in that sort of behaviour. Anyone can have 'a little moment of vanity'. |
| 4129 | It is self-evident (from the point of view of the Universe) that no individual has more importance than another [Sidgwick] |
| Full Idea: It is a self-evident principle that the good of one individual is of no more importance, from the point of view of the Universe, than the good of any other, ..and as a rational being I am bound to aim at good generally, not merely at a particular part. | |
| From: Henry Sidgwick (The Methods of Ethics (7th edn) [1874], III.XIII.3) | |
| A reaction: Showing that even a very empirical theory like utilitarianism has an a priori basis. Of course, the principle is false. What about animals, the senile, criminals, androids? What bestows 'importance'? |
| 20588 | Sidwick argues for utilitarian institutions, rather than actions [Sidgwick, by Tuckness/Wolf] |
| Full Idea: Sidgwick's complex version of utilitarianism urges that institutions should be set in place to maximise utility, but that individual actions people undertake might not appear to be justifiable on utilitarian terms. | |
| From: report of Henry Sidgwick (The Methods of Ethics (7th edn) [1874]) by Tuckness,A/Wolf,C - This is Political Philosophy 1 Refs | |
| A reaction: This seems to be a specifically political version of utilitarianism, but isn't cited much by political philosophers who discuss utilitarianism. |