34 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] |
468 | Musical performance can reveal a range of virtues [Damon of Ath.] |
18648 | Freedom to live according to our own conception of the good is the ultimate value [Nozick, by Kymlicka] |
20585 | If an experience machine gives you any experience you want, should you hook up for life? [Nozick] |
18643 | A minimal state should protect, but a state forcing us to do more is unjustified [Nozick] |
18642 | Individual rights are so strong that the state and its officials must be very limited in power [Nozick] |
18644 | States can't enforce mutual aid on citizens, or interfere for their own good [Nozick] |
22661 | My Anarchy, State and Utopia neglected our formal social ties and concerns [Nozick on Nozick] |
18641 | If people hold things legitimately, just distribution is simply the result of free exchanges [Nozick, by Kymlicka] |
20539 | Property is legitimate by initial acquisition, voluntary transfer, or rectification of injustice [Nozick, by Swift] |
18645 | Nozick assumes initial holdings include property rights, but we can challenge that [Kymlicka on Nozick] |
20521 | Can I come to own the sea, by mixing my private tomato juice with it? [Nozick] |
18646 | How did the private property get started? If violence was involved, we can redistribute it [Kymlicka on Nozick] |
18647 | If property is only initially acquired by denying the rights of others, Nozick can't get started [Kymlicka on Nozick] |
21737 | Unowned things may be permanently acquired, if it doesn't worsen the position of other people [Nozick] |
21738 | Maybe land was originally collectively owned, rather than unowned? [Cohen,GA on Nozick] |