20 ideas
13939 | No possible evidence could decide the reality of numbers, so it is a pseudo-question [Carnap] |
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] |
13936 | Questions about numbers are answered by analysis, and are analytic, and hence logically true [Carnap] |
8748 | Logical positivists incorporated geometry into logicism, saying axioms are just definitions [Carnap, by Shapiro] |
8960 | Internal questions about abstractions are trivial, and external ones deeply problematic [Carnap, by Szabó] |
13933 | Existence questions are 'internal' (within a framework) or 'external' (concerning the whole framework) [Carnap] |
13934 | To be 'real' is to be an element of a system, so we cannot ask reality questions about the system itself [Carnap] |
13938 | A linguistic framework involves commitment to entities, so only commitment to the framework is in question [Carnap] |
13935 | We only accept 'things' within a language with formation, testing and acceptance rules [Carnap] |
13932 | Empiricists tend to reject abstract entities, and to feel sympathy with nominalism [Carnap] |
13937 | New linguistic claims about entities are not true or false, but just expedient, fruitful or successful [Carnap] |
13940 | All linguistic forms in science are merely judged by their efficiency as instruments [Carnap] |
1863 | If the soul achieves well-being in another life, it doesn't follow that I do [Aquinas] |