33 ideas
20728 | Metaphysics is hopeless with its present epistemology; common-sense realism is needed [Colvin] |
22138 | Science rests on scholastic metaphysics, not on Hume, Kant or Carnap [Boulter] |
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] |
20726 | We can only distinguish self from non-self if there is an inflexible external reality [Colvin] |
20727 | Common-sense realism rests on our interests and practical life [Colvin] |
20730 | If objects are doubted because their appearances change, that presupposes one object [Colvin] |
20729 | Arguments that objects are unknowable or non-existent assume the knower's existence [Colvin] |
20731 | The idea that everything is relations is contradictory; relations are part of the concept of things [Colvin] |
22134 | Thoughts are general, but the world isn't, so how can we think accurately? [Boulter] |
22150 | Logical possibility needs the concepts of the proposition to be adequate [Boulter] |
22139 | Experiments don't just observe; they look to see what interventions change the natural order [Boulter] |
22136 | Science begins with sufficient reason, de-animation, and the importance of nature [Boulter] |
22135 | Our concepts can never fully capture reality, but simplification does not falsify [Boulter] |
22152 | Aristotelians accept the analytic-synthetic distinction [Boulter] |
22156 | The facts about human health are the measure of the values in our lives [Boulter] |