17 ideas
291 | Don't assume that wisdom is the automatic consequence of old age [Plato] |
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] |
9837 | 0 is not a number, as it answers 'how many?' negatively [Husserl, by Dummett] |
9576 | Multiplicity in general is just one and one and one, etc. [Husserl] |
17444 | Husserl said counting is more basic than Frege's one-one correspondence [Husserl, by Heck] |
10286 | A 'set' is a mathematically well-behaved class [Hodges,W] |
9575 | Husserl identifies a positive mental act of unification, and a negative mental act for differences [Husserl, by Frege] |
21214 | We clarify concepts (e.g. numbers) by determining their psychological origin [Husserl, by Velarde-Mayol] |
9819 | Psychologism blunders in focusing on concept-formation instead of delineating the concepts [Dummett on Husserl] |
9851 | Husserl wanted to keep a shadowy remnant of abstracted objects, to correlate them [Dummett on Husserl] |
293 | Being unafraid (perhaps through ignorance) and being brave are two different things [Plato] |