22 ideas
10282 | Logic is the study of sound argument, or of certain artificial languages (or applying the latter to the former) [Hodges,W] |
11211 | If a sound conclusion comes from two errors that cancel out, the path of the argument must matter [Rumfitt] |
11210 | Standardly 'and' and 'but' are held to have the same sense by having the same truth table [Rumfitt] |
11212 | The sense of a connective comes from primitively obvious rules of inference [Rumfitt] |
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] |
23664 | Powers are quite distinct and simple, and so cannot be defined [Reid] |
23669 | Thinkers say that matter has intrinsic powers, but is also passive and acted upon [Reid] |
23666 | It is obvious that there could not be a power without a subject which possesses it [Reid] |
23665 | Consciousness is the power of mind to know itself, and minds are grounded in powers [Reid] |
23668 | Our own nature attributes free determinations to our own will [Reid] |
11214 | We learn 'not' along with affirmation, by learning to either affirm or deny a sentence [Rumfitt] |
20051 | Reid said that agent causation is a unique type of causation [Reid, by Stout,R] |
8383 | Day and night are constantly conjoined, but they don't cause one another [Reid, by Crane] |
23667 | Regular events don't imply a cause, without an innate conviction of universal causation [Reid] |
23670 | Scientists don't know the cause of magnetism, and only discover its regulations [Reid] |
23671 | Laws are rules for effects, but these need a cause; rules of navigation don't navigate [Reid] |