12 ideas
10282 | Logic is the study of sound argument, or of certain artificial languages (or applying the latter to the former) [Hodges,W] |
10283 | A formula needs an 'interpretation' of its constants, and a 'valuation' of its variables [Hodges,W] |
10284 | There are three different standard presentations of semantics [Hodges,W] |
10285 | I |= φ means that the formula φ is true in the interpretation I [Hodges,W] |
10288 | Down Löwenheim-Skolem: if a countable language has a consistent theory, that has a countable model [Hodges,W] |
10289 | Up Löwenheim-Skolem: if infinite models, then arbitrarily large models [Hodges,W] |
10287 | If a first-order theory entails a sentence, there is a finite subset of the theory which entails it [Hodges,W] |
10286 | A 'set' is a mathematically well-behaved class [Hodges,W] |
19087 | The meaning or purport of a symbol is all the rational conduct it would lead to [Peirce] |
20420 | The emotion expressed is non-conscious, but feels oppressive until expression relieves it [Collingwood] |
20421 | Art exists ideally, purely as experiences in the mind of the perceiver [Collingwood, by Kemp] |
20406 | Art clarifies the artist's mind and feelings, thus leading to self-knowledge [Collingwood, by Davies,S] |