32 ideas
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] |
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] |
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] |
7720 | Two things can only resemble one another in some respect, and that may reintroduce a universal [Lowe] |
7712 | On substances, Leibniz emphasises unity, Spinoza independence, Locke relations to qualities [Lowe] |
15959 | If the substantial form of brass implies its stability, how can it melt and remain brass? [Alexander,P] |
15956 | The peripatetics treated forms and real qualities as independent of matter, and non-material [Alexander,P] |
7710 | Perception is a mode of belief-acquisition, and does not involve sensation [Lowe] |
7711 | Science requires a causal theory - perception of an object must be an experience caused by the object [Lowe] |
15975 | Can the qualities of a body be split into two groups, where the smaller explains the larger? [Alexander,P] |
7714 | Personal identity is a problem across time (diachronic) and at an instant (synchronic) [Lowe] |
7715 | Mentalese isn't a language, because it isn't conventional, or a means of public communication [Lowe] |
7722 | If meaning is mental pictures, explain "the cat (or dog!) is NOT on the mat" [Lowe] |
15963 | Science has been partly motivated by the belief that the universe is run by God's laws [Alexander,P] |
15951 | Alchemists tried to separate out essences, which influenced later chemistry [Alexander,P] |
15981 | Absolute space either provides locations, or exists but lacks 'marks' for locations [Alexander,P] |