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] |
16756 | Substantial forms must exist, to explain the stability of metals like silver and tin [Albertus Magnus] |
16718 | Primary qualities are the cause of all the other sensible qualities [Albertus Magnus] |
7439 | The qualities involved in sensations are entirely intentional [Anscombe, by Armstrong] |
8353 | Freedom involves acting according to an idea [Anscombe] |
8352 | To believe in determinism, one must believe in a system which determines events [Anscombe] |
20041 | Intentional actions are those which are explained by giving the reason for so acting [Anscombe] |
8070 | It would be better to point to failings of character, than to moral wrongness of actions [Anscombe] |
8065 | 'Ought' and 'right' are survivals from earlier ethics, and should be jettisoned [Anscombe] |
8069 | Between Aristotle and us, a Judaeo-Christian legal conception of ethics was developed [Anscombe] |
8351 | With diseases we easily trace a cause from an effect, but we cannot predict effects [Anscombe] |
4777 | The word 'cause' is an abstraction from a group of causal terms in a language (scrape, push..) [Anscombe] |
10363 | Causation is relative to how we describe the primary relata [Anscombe, by Schaffer,J] |
8350 | Since Mill causation has usually been explained by necessary and sufficient conditions [Anscombe] |