76 ideas
9955 | Contextual definitions replace a complete sentence containing the expression [George/Velleman] |
10031 | Impredicative definitions quantify over the thing being defined [George/Velleman] |
10098 | The 'power set' of A is all the subsets of A [George/Velleman] |
10099 | The 'ordered pair' <a, b>, for two sets a and b, is the set {{a, b},{a}} [George/Velleman] |
10101 | Cartesian Product A x B: the set of all ordered pairs in which a∈A and b∈B [George/Velleman] |
10103 | Grouping by property is common in mathematics, usually using equivalence [George/Velleman] |
10104 | 'Equivalence' is a reflexive, symmetric and transitive relation; 'same first letter' partitions English words [George/Velleman] |
10096 | Even the elements of sets in ZFC are sets, resting on the pure empty set [George/Velleman] |
10097 | Axiom of Extensionality: for all sets x and y, if x and y have the same elements then x = y [George/Velleman] |
10100 | Axiom of Pairing: for all sets x and y, there is a set z containing just x and y [George/Velleman] |
17900 | The Axiom of Reducibility made impredicative definitions possible [George/Velleman] |
10109 | ZFC can prove that there is no set corresponding to the concept 'set' [George/Velleman] |
10108 | As a reduction of arithmetic, set theory is not fully general, and so not logical [George/Velleman] |
10111 | Asserting Excluded Middle is a hallmark of realism about the natural world [George/Velleman] |
16489 | Is it possible to state every possible truth about the whole course of nature without using 'not'? [Russell] |
10129 | A 'model' is a meaning-assignment which makes all the axioms true [George/Velleman] |
10105 | Differences between isomorphic structures seem unimportant [George/Velleman] |
10119 | Consistency is a purely syntactic property, unlike the semantic property of soundness [George/Velleman] |
10126 | A 'consistent' theory cannot contain both a sentence and its negation [George/Velleman] |
10120 | Soundness is a semantic property, unlike the purely syntactic property of consistency [George/Velleman] |
10127 | A 'complete' theory contains either any sentence or its negation [George/Velleman] |
10106 | Rational numbers give answers to division problems with integers [George/Velleman] |
10102 | The integers are answers to subtraction problems involving natural numbers [George/Velleman] |
10107 | Real numbers provide answers to square root problems [George/Velleman] |
9946 | Logicists say mathematics is applicable because it is totally general [George/Velleman] |
10125 | The classical mathematician believes the real numbers form an actual set [George/Velleman] |
17899 | Second-order induction is stronger as it covers all concepts, not just first-order definable ones [George/Velleman] |
10128 | The Incompleteness proofs use arithmetic to talk about formal arithmetic [George/Velleman] |
17902 | A successor is the union of a set with its singleton [George/Velleman] |
10133 | Frege's Theorem shows the Peano Postulates can be derived from Hume's Principle [George/Velleman] |
10130 | Set theory can prove the Peano Postulates [George/Velleman] |
10089 | Talk of 'abstract entities' is more a label for the problem than a solution to it [George/Velleman] |
10131 | If mathematics is not about particulars, observing particulars must be irrelevant [George/Velleman] |
10092 | In the unramified theory of types, the types are objects, then sets of objects, sets of sets etc. [George/Velleman] |
10094 | The theory of types seems to rule out harmless sets as well as paradoxical ones. [George/Velleman] |
10095 | Type theory has only finitely many items at each level, which is a problem for mathematics [George/Velleman] |
17901 | Type theory prohibits (oddly) a set containing an individual and a set of individuals [George/Velleman] |
10114 | Bounded quantification is originally finitary, as conjunctions and disjunctions [George/Velleman] |
10134 | Much infinite mathematics can still be justified finitely [George/Velleman] |
10123 | The intuitionists are the idealists of mathematics [George/Velleman] |
10124 | Gödel's First Theorem suggests there are truths which are independent of proof [George/Velleman] |
16490 | Some facts about experience feel like logical necessities [Russell] |
16488 | It is hard to explain how a sentence like 'it is not raining' can be found true by observation [Russell] |
4363 | The word 'person' is useless in ethics, because what counts as a good or bad self-conscious being? [Hursthouse] |
10110 | Corresponding to every concept there is a class (some of them sets) [George/Velleman] |
16491 | If we define 'this is not blue' as disbelief in 'this is blue', we eliminate 'not' as an ingredient of facts [Russell] |
4355 | There may be inverse akrasia, where the agent's action is better than their judgement recommends [Hursthouse] |
4325 | Must all actions be caused in part by a desire, or can a belief on its own be sufficient? [Hursthouse] |
4351 | It is a fantasy that only through the study of philosophy can one become virtuous [Hursthouse] |
4340 | You are not a dishonest person if a tragic dilemma forces you to do something dishonest [Hursthouse] |
4329 | After a moral dilemma is resolved there is still a 'remainder', requiring (say) regret [Hursthouse] |
4330 | Deontologists resolve moral dilemmas by saying the rule conflict is merely apparent [Hursthouse] |
4341 | Involuntary actions performed in tragic dilemmas are bad because they mar a good life [Hursthouse] |
4358 | Virtue may be neither sufficient nor necessary for eudaimonia [Hursthouse] |
4337 | Teenagers are often quite wise about ideals, but rather stupid about consequences [Hursthouse] |
4324 | Animals and plants can 'flourish', but only rational beings can have eudaimonia [Hursthouse] |
4359 | When it comes to bringing up children, most of us think that the virtues are the best bet [Hursthouse] |
4336 | Any strict ranking of virtues or rules gets abandoned when faced with particular cases [Hursthouse] |
4334 | Virtue ethics is open to the objection that it fails to show priority among the virtues [Hursthouse] |
4361 | Good animals can survive, breed, feel characteristic pleasure and pain, and contribute to the group [Hursthouse] |
4349 | Virtuous people may not be fully clear about their reasons for action [Hursthouse] |
4352 | Performing an act simply because it is virtuous is sufficient to be 'morally motivated' or 'dutiful' [Hursthouse] |
4353 | If moral motivation is an all-or-nothing sense of duty, how can children act morally? [Hursthouse] |
4346 | The emotions of sympathy, compassion and love are no guarantee of right action or acting well [Hursthouse] |
4339 | According to virtue ethics, two agents may respond differently, and yet both be right [Hursthouse] |
4354 | Maybe in a deeply poisoned character none of their milder character traits could ever be a virtue [Hursthouse] |
4364 | Being unusually virtuous in some areas may entail being less virtuous in others [Hursthouse] |
4356 | We are puzzled by a person who can show an exceptional virtue and also behave very badly [Hursthouse] |
4327 | Deontologists do consider consequences, because they reveal when a rule might apply [Hursthouse] |
4335 | 'Codifiable' morality give rules for decisions which don't require wisdom [Hursthouse] |
4328 | Preference utilitarianism aims to be completely value-free, or empirical [Hursthouse] |
4343 | We are torn between utilitarian and deontological views of lying, depending on the examples [Hursthouse] |
4338 | Deontologists usually accuse utilitarians of oversimplifying hard cases [Hursthouse] |
4365 | We are distinct from other animals in behaving rationally - pursuing something as good, for reasons [Hursthouse] |
4786 | Russell's 'at-at' theory says motion is to be at the intervening points at the intervening instants [Russell, by Psillos] |
4350 | If people are virtuous in obedience to God, would they become wicked if they lost their faith? [Hursthouse] |