27 ideas
10476 | The idea that groups of concepts could be 'implicitly defined' was abandoned [Hodges,W] |
10282 | Logic is the study of sound argument, or of certain artificial languages (or applying the latter to the former) [Hodges,W] |
10478 | Since first-order languages are complete, |= and |- have the same meaning [Hodges,W] |
10477 | |= in model-theory means 'logical consequence' - it holds in all models [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] |
10474 | |= should be read as 'is a model for' or 'satisfies' [Hodges,W] |
10473 | Model theory studies formal or natural language-interpretation using set-theory [Hodges,W] |
10475 | A 'structure' is an interpretation specifying objects and classes of quantification [Hodges,W] |
10481 | Models in model theory are structures, not sets of descriptions [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] |
10480 | First-order logic can't discriminate between one infinite cardinal and another [Hodges,W] |
10286 | A 'set' is a mathematically well-behaved class [Hodges,W] |
7096 | We may still admire a person's character even if the traits are involuntary [Statman] |
7098 | There is a new sort of moral scepticism, about the possibility of moral theories [Statman] |
7099 | With a broad concept of flourishing, it might be possible without the virtues [Statman] |
7100 | Virtue theory isn't a genuine ethical theory, because it doesn't have universal application [Statman] |
7102 | Promises create moral duties that have nothing to do with character [Statman] |
7095 | Moral education is better by concrete example than abstract principle [Statman] |
7094 | Friends express friendship even when no utility is involved [Statman] |
7093 | Behaviour may be disgusting or inhumane, but violate no duty [Statman] |
7104 | The ancients recognised imperfect duties, but we have added perfect duties like justice [Statman] |
7103 | Abortion issues focus on the mother's right over her body, and the status of the foetus [Statman] |
6005 | Animals are dangerous and nourishing, and can't form contracts of justice [Hermarchus, by Sedley] |