62 ideas
23728 | Analysis aims to express the full set of platitudes surrounding a given concept [Smith,M] |
23744 | Defining a set of things by paradigms doesn't pin them down enough [Smith,M] |
8721 | An 'impredicative' definition seems circular, because it uses the term being defined [Friend] |
8680 | Classical definitions attempt to refer, but intuitionist/constructivist definitions actually create objects [Friend] |
3678 | Reductio ad absurdum proves an idea by showing that its denial produces contradiction [Friend] |
8705 | Anti-realists see truth as our servant, and epistemically contrained [Friend] |
8713 | In classical/realist logic the connectives are defined by truth-tables [Friend] |
8708 | Double negation elimination is not valid in intuitionist logic [Friend] |
8694 | Free logic was developed for fictional or non-existent objects [Friend] |
8665 | A 'proper subset' of A contains only members of A, but not all of them [Friend] |
8672 | A 'powerset' is all the subsets of a set [Friend] |
8677 | Set theory makes a minimum ontological claim, that the empty set exists [Friend] |
8666 | Infinite sets correspond one-to-one with a subset [Friend] |
8682 | Major set theories differ in their axioms, and also over the additional axioms of choice and infinity [Friend] |
8709 | The law of excluded middle is syntactic; it just says A or not-A, not whether they are true or false [Friend] |
8711 | Intuitionists read the universal quantifier as "we have a procedure for checking every..." [Friend] |
8675 | Paradoxes can be solved by talking more loosely of 'classes' instead of 'sets' [Friend] |
8674 | The Burali-Forti paradox asks whether the set of all ordinals is itself an ordinal [Friend] |
8667 | The 'integers' are the positive and negative natural numbers, plus zero [Friend] |
8668 | The 'rational' numbers are those representable as fractions [Friend] |
8670 | A number is 'irrational' if it cannot be represented as a fraction [Friend] |
8661 | The natural numbers are primitive, and the ordinals are up one level of abstraction [Friend] |
8664 | Cardinal numbers answer 'how many?', with the order being irrelevant [Friend] |
8671 | The 'real' numbers (rationals and irrationals combined) is the Continuum, which has no gaps [Friend] |
8663 | Raising omega to successive powers of omega reveal an infinity of infinities [Friend] |
8662 | The first limit ordinal is omega (greater, but without predecessor), and the second is twice-omega [Friend] |
8669 | Between any two rational numbers there is an infinite number of rational numbers [Friend] |
8676 | Is mathematics based on sets, types, categories, models or topology? [Friend] |
8678 | Most mathematical theories can be translated into the language of set theory [Friend] |
8701 | The number 8 in isolation from the other numbers is of no interest [Friend] |
8702 | In structuralism the number 8 is not quite the same in different structures, only equivalent [Friend] |
8699 | Are structures 'ante rem' (before reality), or are they 'in re' (grounded in physics)? [Friend] |
8696 | Structuralist says maths concerns concepts about base objects, not base objects themselves [Friend] |
8695 | Structuralism focuses on relations, predicates and functions, with objects being inessential [Friend] |
8700 | 'In re' structuralism says that the process of abstraction is pattern-spotting [Friend] |
8681 | The big problem for platonists is epistemic: how do we perceive, intuit, know or detect mathematical facts? [Friend] |
8712 | Mathematics should be treated as true whenever it is indispensable to our best physical theory [Friend] |
8716 | Formalism is unconstrained, so cannot indicate importance, or directions for research [Friend] |
8706 | Constructivism rejects too much mathematics [Friend] |
8707 | Intuitionists typically retain bivalence but reject the law of excluded middle [Friend] |
8704 | Structuralists call a mathematical 'object' simply a 'place in a structure' [Friend] |
8685 | Studying biology presumes the laws of chemistry, and it could never contradict them [Friend] |
23743 | Capturing all the common sense facts about rationality is almost impossible [Smith,M] |
8688 | Concepts can be presented extensionally (as objects) or intensionally (as a characterization) [Friend] |
23723 | In the Humean account, desires are not true/false, or subject to any rational criticism [Smith,M] |
23735 | Subjects may be fallible about the desires which explain their actions [Smith,M] |
23736 | A person can have a desire without feeling it [Smith,M] |
23739 | Goals need desires, and so only desires can motivate us [Smith,M] |
23738 | Humeans (unlike their opponents) say that desires and judgements can separate [Smith,M] |
23742 | If first- and second-order desires conflict, harmony does not require the second-order to win [Smith,M] |
23746 | Objective reasons to act might be the systematic desires of a fully rational person [Smith,M] |
23724 | A pure desire could be criticised if it were based on a false belief [Smith,M] |
23733 | Motivating reasons are psychological, while normative reasons are external [Smith,M] |
23740 | Humeans take maximising desire satisfaction as the normative reasons for actions [Smith,M] |
23745 | We cannot expect even fully rational people to converge on having the same desires for action [Smith,M] |
468 | Musical performance can reveal a range of virtues [Damon of Ath.] |
23731 | 'Externalists' say moral judgements are not reasons, and maybe not even motives [Smith,M] |
23732 | A person could make a moral judgement without being in any way motivated by it [Smith,M] |
23729 | Moral internalism says a judgement of rightness is thereby motivating [Smith,M] |
23730 | 'Rationalism' says the rightness of an action is a reason to perform it [Smith,M] |
23727 | Expressivists count attitudes as 'moral' if they concern features of things, rather than their mere existence [Smith,M] |
23741 | Is valuing something a matter of believing or a matter of desiring? [Smith,M] |