13 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] |
| 20508 | How people vote should be on public record, so they can be held accountable [Mill, by Wolff,J] |
| 20507 | Voting is a strict duty, like jury service, and must only be aimed at the public good [Mill] |
| 20505 | Direct democracy is inexperience judging experience, and ignorance judging knowledge [Mill] |
| 20504 | People can only participate in decisions in small communities, so representatives are needed [Mill] |