37 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] |
| 17292 | Avoid 'in virtue of' for grounding, since it might imply a reflexive relation such as identity [Audi,P] |
| 17295 | Ground relations depend on the properties [Audi,P] |
| 17297 | A ball's being spherical non-causally determines its power to roll [Audi,P] |
| 17302 | Ground is irreflexive, asymmetric, transitive, non-monotonic etc. [Audi,P] |
| 17303 | The best critique of grounding says it is actually either identity or elimination [Audi,P] |
| 17294 | Grounding is a singular relation between worldly facts [Audi,P] |
| 17300 | If grounding relates facts, properties must be included, as well as objects [Audi,P] |
| 17296 | We must accept grounding, for our important explanations [Audi,P] |
| 17301 | Reduction is just identity, so the two things are the same fact, so reduction isn't grounding [Audi,P] |
| 17293 | Worldly facts are obtaining states of affairs, with constituents; conceptual facts also depend on concepts [Audi,P] |
| 17298 | Two things being identical (like water and H2O) is not an explanation [Audi,P] |
| 17299 | There are plenty of examples of non-causal explanation [Audi,P] |
| 2854 | Prescriptivism says 'ought' without commitment to act is insincere, or weakly used [Hooker,B] |
| 2856 | Universal moral judgements imply the Golden Rule ('do as you would be done by') [Hooker,B] |
| 20883 | Modern utilitarians value knowledge, friendship, autonomy, and achievement, as well as pleasure [Hooker,B] |
| 20884 | Rule-utilitarians prevent things like torture, even on rare occasions when it seems best [Hooker,B] |
| 20885 | Euthanasia is active or passive, and voluntary, non-voluntary or involuntary [Hooker,B] |
| 20882 | Euthanasia may not involve killing, so it is 'killing or not saving, out of concern for that person' [Hooker,B] |