18 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] |
10289 | Up Löwenheim-Skolem: if infinite models, then arbitrarily large models [Hodges,W] |
10288 | Down Löwenheim-Skolem: if a countable language has a consistent theory, that has a countable model [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] |
15566 | Events are classes, and so there is a mereology of their parts [Lewis] |
15567 | Some events involve no change; they must, because causal histories involve unchanges [Lewis] |
15561 | The events that suit semantics may not be the events that suit causation [Lewis] |
15565 | Events have inbuilt essences, as necessary conditions for their occurrence [Lewis] |
15564 | An event is a property of a unique space-time region [Lewis] |
15563 | Properties are very abundant (unlike universals), and are used for semantics and higher-order variables [Lewis] |
5049 | Intelligent pleasure is the perception of beauty, order and perfection [Leibniz] |
15562 | Causation is a general relation derived from instances of causal dependence [Lewis] |
5048 | Perfection is simply quantity of reality [Leibniz] |
5050 | Evil serves a greater good, and pain is necessary for higher pleasure [Leibniz] |