25 ideas
20728 | Metaphysics is hopeless with its present epistemology; common-sense realism is needed [Colvin] |
10775 | The axiom of choice now seems acceptable and obvious (if it is meaningful) [Tharp] |
21563 | The 'no classes' theory says the propositions just refer to the members [Russell] |
10766 | Logic is either for demonstration, or for characterizing structures [Tharp] |
10767 | Elementary logic is complete, but cannot capture mathematics [Tharp] |
10769 | Second-order logic isn't provable, but will express set-theory and classic problems [Tharp] |
10762 | In sentential logic there is a simple proof that all truth functions can be reduced to 'not' and 'and' [Tharp] |
10776 | The main quantifiers extend 'and' and 'or' to infinite domains [Tharp] |
10774 | There are at least five unorthodox quantifiers that could be used [Tharp] |
10773 | The Löwenheim-Skolem property is a limitation (e.g. can't say there are uncountably many reals) [Tharp] |
10777 | Skolem mistakenly inferred that Cantor's conceptions were illusory [Tharp] |
10765 | Soundness would seem to be an essential requirement of a proof procedure [Tharp] |
10763 | Completeness and compactness together give axiomatizability [Tharp] |
10770 | If completeness fails there is no algorithm to list the valid formulas [Tharp] |
10771 | Compactness is important for major theories which have infinitely many axioms [Tharp] |
10772 | Compactness blocks infinite expansion, and admits non-standard models [Tharp] |
10764 | A complete logic has an effective enumeration of the valid formulas [Tharp] |
10768 | Effective enumeration might be proved but not specified, so it won't guarantee knowledge [Tharp] |
21565 | Richard's puzzle uses the notion of 'definition' - but that cannot be defined [Russell] |
21564 | Vicious Circle: what involves ALL must not be one of those ALL [Russell] |
20726 | We can only distinguish self from non-self if there is an inflexible external reality [Colvin] |
20727 | Common-sense realism rests on our interests and practical life [Colvin] |
20730 | If objects are doubted because their appearances change, that presupposes one object [Colvin] |
20729 | Arguments that objects are unknowable or non-existent assume the knower's existence [Colvin] |
20731 | The idea that everything is relations is contradictory; relations are part of the concept of things [Colvin] |