19 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] |
| 23429 | The environment needs localised politics, with its care for the land [Dobson] |
| 23424 | An ideology judges things now, and offers an ideal, with a strategy for reaching it [Dobson] |
| 23426 | Ecologism is often non-liberal, by claiming to know other people's best interests [Dobson] |
| 23427 | Socialism can be productive and centralised, or less productive and decentralised [Dobson] |
| 23428 | Difference feminists say women differ fundamentally from men [Dobson] |
| 23422 | For the environment, affluence and technology matter as much as population size [Dobson] |
| 23425 | Ecologism says growth must be reduced, and efficiency is not enough [Dobson] |
| 23430 | A million years is a proper unit of political time [Dobson] |
| 23423 | We currently value the present fourteen times more highly than the future [Dobson] |
| 1748 | Archelaus was the first person to say that the universe is boundless [Archelaus, by Diog. Laertius] |
| 5989 | Archelaus said life began in a primeval slime [Archelaus, by Schofield] |