18 ideas
| 9108 | From an impossibility anything follows [William of Ockham] |
| 9107 | A proposition is true if its subject and predicate stand for the same thing [William of Ockham] |
| 16300 | Ockham had an early axiomatic account of truth [William of Ockham, by Halbach] |
| 10282 | Logic is the study of sound argument, or of certain artificial languages (or applying the latter to the former) [Hodges,W] |
| 9106 | The word 'every' only signifies when added to a term such as 'man', referring to all men [William of Ockham] |
| 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] |
| 9113 | Just as unity is not a property of a single thing, so numbers are not properties of many things [William of Ockham] |
| 9110 | The words 'thing' and 'to be' assert the same idea, as a noun and as a verb [William of Ockham] |
| 15388 | Universals are single things, and only universal in what they signify [William of Ockham] |
| 9109 | If essence and existence were two things, one could exist without the other, which is impossible [William of Ockham] |
| 9105 | Some concepts for propositions exist only in the mind, and in no language [William of Ockham] |
| 468 | Musical performance can reveal a range of virtues [Damon of Ath.] |