52 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] |
| 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] |
| 16668 | Modes of things exist in some way, without being full-blown substances [Gassendi] |
| 16730 | If matter is entirely atoms, anything else we notice in it can only be modes [Gassendi] |
| 16619 | We observe qualities, and use 'induction' to refer to the substances lying under them [Gassendi] |
| 3400 | Things must have parts to intermingle [Gassendi] |
| 22849 | Rawls's theory cannot justify liberalism, since it presupposes free and equal participants [Charvet] |
| 22848 | People with strong prior beliefs would have nothing to do with a veil of ignorance [Charvet] |
| 22838 | Societies need shared values, so conservatism is right if rational discussion of values is impossible [Charvet] |
| 22846 | The universalism of utilitarianism implies a world state [Charvet] |
| 22835 | Liberals value freedom and equality, but the society itself must decide on its values [Charvet] |
| 22831 | Modern libertarian societies still provide education and some housing [Charvet] |
| 22839 | Liberalism needs people to either have equal autonomy, or everyone to have enough autonomy [Charvet] |
| 22847 | Kant places a higher value on the universal rational will than on the people asserting it [Charvet] |
| 22821 | Liberalism asserts maximum freedom, but that must be equal for all participants [Charvet] |
| 22834 | Egalitarian liberals prefer equality (either of input or outcome) to liberty [Charvet] |
| 22822 | Liberals promote community and well-being - because all good societies need them [Charvet] |
| 22841 | Identity multiculturalism emerges from communitarianism, preferring community to humanity [Charvet] |
| 22842 | For communitarians it seems that you must accept the culture you are born into [Charvet] |
| 22830 | Give by ability and receive by need, rather than a free labour market [Charvet] |
| 22829 | Allowing defamatory speech is against society's interests, by blurring which people are trustworthy [Charvet] |
| 22836 | 'Freedom from' is an empty idea, if the freedom is not from impediments to my desires [Charvet] |
| 22837 | Positive freedom can lead to coercion, if you are forced to do what you chose to do [Charvet] |
| 22844 | First level autonomy is application of personal values; second level is criticising them [Charvet] |
| 22840 | Mere equality, as in two trees being the same height, has no value at all [Charvet] |
| 22843 | Inequalities are worse if they seem to be your fault, rather than social facts [Charvet] |
| 22845 | Money allows unlimited inequalities, and we obviously all agree to money [Charvet] |
| 22828 | The rule of law mainly benefits those with property and liberties [Charvet] |
| 22825 | The 1689 Bill of Rights denied the monarch new courts, or the right to sit as judge [Charvet] |
| 22823 | The rule of law is mainly to restrict governments [Charvet] |
| 22827 | Justice superior to the rule of law is claimed on behalf of the workers, or the will of the nation [Charvet] |
| 22826 | From 1701 only parliament could remove judges, whose decisions could not be discussed [Charvet] |
| 22832 | Welfare is needed if citizens are to accept the obligations of a liberal state [Charvet] |
| 16593 | Atoms are not points, but hard indivisible things, which no force in nature can divide [Gassendi] |
| 16729 | How do mere atoms produce qualities like colour, flavour and odour? [Gassendi] |