33 ideas
23531 | Philosophers should interpret the world, by expressing its possibilities [Berardi] |
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] |
23538 | Nothingness only exists in consciousness [Berardi] |
20475 | Maybe modal sentences cannot be true or false [Casullo] |
20476 | If the necessary is a priori, so is the contingent, because the same evidence is involved [Casullo] |
20471 | Epistemic a priori conditions concern either the source, defeasibility or strength [Casullo] |
20477 | The main claim of defenders of the a priori is that some justifications are non-experiential [Casullo] |
20472 | Analysis of the a priori by necessity or analyticity addresses the proposition, not the justification [Casullo] |
20474 | 'Overriding' defeaters rule it out, and 'undermining' defeaters weaken in [Casullo] |
23532 | The delusion of free will brings a sense of guilt [Berardi] |
23537 | American white men trusted the philosophy of winning, and then discovered losing [Berardi] |
23536 | Community is now a nostalgic memory, which no longer exists [Berardi] |
23534 | Communism failed to unite western workers with the oppressed of the south [Berardi] |
23533 | The economy has replaced medieval theocracy at the centre of our society [Berardi] |
23535 | Western workers turn to nationalism, to avert the effects of globalisation [Berardi] |