54 ideas
| 23269 | Philosophy must start from clearly observed facts [Galen] |
| 23248 | Early empiricists said reason was just a useless concept introduced by philosophers [Galen, by Frede,M] |
| 13520 | A 'tautology' must include connectives [Wolf,RS] |
| 13524 | Deduction Theorem: T∪{P}|-Q, then T|-(P→Q), which justifies Conditional Proof [Wolf,RS] |
| 13522 | Universal Generalization: If we prove P(x) with no special assumptions, we can conclude ∀xP(x) [Wolf,RS] |
| 13521 | Universal Specification: ∀xP(x) implies P(t). True for all? Then true for an instance [Wolf,RS] |
| 13523 | Existential Generalization (or 'proof by example'): if we can say P(t), then we can say something is P [Wolf,RS] |
| 13529 | Empty Set: ∃x∀y ¬(y∈x). The unique empty set exists [Wolf,RS] |
| 13526 | Comprehension Axiom: if a collection is clearly specified, it is a set [Wolf,RS] |
| 10405 | In the iterative conception of sets, they form a natural hierarchy [Swoyer] |
| 13534 | In first-order logic syntactic and semantic consequence (|- and |=) nicely coincide [Wolf,RS] |
| 13535 | First-order logic is weakly complete (valid sentences are provable); we can't prove every sentence or its negation [Wolf,RS] |
| 10407 | Logical Form explains differing logical behaviour of similar sentences [Swoyer] |
| 13531 | Model theory reveals the structures of mathematics [Wolf,RS] |
| 13532 | Model theory 'structures' have a 'universe', some 'relations', some 'functions', and some 'constants' [Wolf,RS] |
| 13519 | Model theory uses sets to show that mathematical deduction fits mathematical truth [Wolf,RS] |
| 13533 | First-order model theory rests on completeness, compactness, and the Löwenheim-Skolem-Tarski theorem [Wolf,RS] |
| 13537 | An 'isomorphism' is a bijection that preserves all structural components [Wolf,RS] |
| 13539 | The LST Theorem is a serious limitation of first-order logic [Wolf,RS] |
| 13538 | If a theory is complete, only a more powerful language can strengthen it [Wolf,RS] |
| 13525 | Most deductive logic (unlike ordinary reasoning) is 'monotonic' - we don't retract after new givens [Wolf,RS] |
| 13530 | An ordinal is an equivalence class of well-orderings, or a transitive set whose members are transitive [Wolf,RS] |
| 13518 | Modern mathematics has unified all of its objects within set theory [Wolf,RS] |
| 14592 | Some abstract things have a beginning and end, so may exist in time (though not space) [Swoyer] |
| 10421 | Supervenience is nowadays seen as between properties, rather than linguistic [Swoyer] |
| 14594 | Ontologists seek existence and identity conditions, and modal and epistemic status for a thing [Swoyer] |
| 10410 | Anti-realists can't explain different methods to measure distance [Swoyer] |
| 10399 | If a property such as self-identity can only be in one thing, it can't be a universal [Swoyer] |
| 10416 | Can properties have parts? [Swoyer] |
| 14595 | Can properties exemplify other properties? [Swoyer] |
| 10417 | There are only first-order properties ('red'), and none of higher-order ('coloured') [Swoyer] |
| 10413 | The best-known candidate for an identity condition for properties is necessary coextensiveness [Swoyer] |
| 10402 | Various attempts are made to evade universals being wholly present in different places [Swoyer] |
| 10400 | Conceptualism says words like 'honesty' refer to concepts, not to properties [Swoyer] |
| 10403 | If properties are abstract objects, then their being abstract exemplifies being abstract [Swoyer] |
| 14593 | Quantum field theory suggests that there are, fundamentally, no individual things [Swoyer] |
| 10406 | One might hope to reduce possible worlds to properties [Swoyer] |
| 10404 | Extreme empiricists can hardly explain anything [Swoyer] |
| 23266 | The spirit in the soul wants freedom, power and honour [Galen] |
| 6003 | Galen showed by experiment that the brain controls the body [Galen, by Hankinson] |
| 23219 | Stopping the heart doesn't terminate activity; pressing the brain does that [Galen, by Cobb] |
| 21799 | We just use the word 'faculty' when we don't know the psychological cause [Galen] |
| 23264 | Philosophers think faculties are in substances, and invent a faculty for every activity [Galen] |
| 23220 | The brain contains memory and reason, and is the source of sensation and decision [Galen] |
| 23265 | The rational part of the soul is the desire for truth, understanding and recollection [Galen] |
| 10408 | Intensions are functions which map possible worlds to sets of things denoted by an expression [Swoyer] |
| 10409 | Research suggests that concepts rely on typical examples [Swoyer] |
| 10401 | The F and G of logic cover a huge range of natural language combinations [Swoyer] |
| 10420 | Maybe a proposition is just a property with all its places filled [Swoyer] |
| 7453 | Galen's medicine followed the mean; each illness was balanced by opposite treatment [Galen, by Hacking] |
| 6030 | Each part of the soul has its virtue - pleasure for appetite, success for competition, and rectitude for reason [Galen] |
| 23268 | We execute irredeemable people, to protect ourselves, as a deterrent, and ending a bad life [Galen] |
| 10412 | If laws are mere regularities, they give no grounds for future prediction [Swoyer] |
| 10411 | Two properties can have one power, and one property can have two powers [Swoyer] |