31 ideas
9283 | Our ancient beliefs can never be overthrown by subtle arguments [Euripides] |
13520 | A 'tautology' must include connectives [Wolf,RS] |
13524 | Deduction Theorem: T∪{P}|-Q, then T|-(P→Q), which justifies Conditional Proof [Wolf,RS] |
13521 | Universal Specification: ∀xP(x) implies P(t). True for all? Then true for an instance [Wolf,RS] |
13522 | Universal Generalization: If we prove P(x) with no special assumptions, we can conclude ∀xP(x) [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] |
13519 | Model theory uses sets to show that mathematical deduction fits mathematical truth [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] |
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] |
12790 | Generalisations must be invariant to explain anything [Leuridan] |
12789 | Biological functions are explained by disposition, or by causal role [Leuridan] |
14386 | Mechanisms are ontologically dependent on regularities [Leuridan] |
12787 | Mechanisms can't explain on their own, as their models rest on pragmatic regularities [Leuridan] |
14384 | We can show that regularities and pragmatic laws are more basic than mechanisms [Leuridan] |
14388 | Mechanisms must produce macro-level regularities, but that needs micro-level regularities [Leuridan] |
14389 | There is nothing wrong with an infinite regress of mechanisms and regularities [Leuridan] |
14387 | Rather than dispositions, functions may be the element that brought a thing into existence [Leuridan] |
14382 | Pragmatic laws allow prediction and explanation, to the extent that reality is stable [Leuridan] |
14385 | Strict regularities are rarely discovered in life sciences [Leuridan] |
14383 | A 'law of nature' is just a regularity, not some entity that causes the regularity [Leuridan] |