20 ideas
13201 | ∈ says the whole set is in the other; ⊆ says the members of the subset are in the other [Enderton] |
13204 | The 'ordered pair' <x,y> is defined to be {{x}, {x,y}} [Enderton] |
13206 | A 'linear or total ordering' must be transitive and satisfy trichotomy [Enderton] |
13200 | Note that {Φ} =/= Φ, because Φ ∈ {Φ} but Φ ∉ Φ [Enderton] |
13199 | The empty set may look pointless, but many sets can be constructed from it [Enderton] |
13203 | The singleton is defined using the pairing axiom (as {x,x}) [Enderton] |
13202 | Fraenkel added Replacement, to give a theory of ordinal numbers [Enderton] |
13205 | We can only define functions if Choice tells us which items are involved [Enderton] |
12215 | The existence of numbers is not a matter of identities, but of constituents of the world [Fine,K] |
12211 | It is plausible that x^2 = -1 had no solutions before complex numbers were 'introduced' [Fine,K] |
12209 | The indispensability argument shows that nature is non-numerical, not the denial of numbers [Fine,K] |
12214 | 'Exists' is a predicate, not a quantifier; 'electrons exist' is like 'electrons spin' [Fine,K] |
12212 | Just as we introduced complex numbers, so we introduced sums and temporal parts [Fine,K] |
12216 | Real objects are those which figure in the facts that constitute reality [Fine,K] |
12218 | Being real and being fundamental are separate; Thales's water might be real and divisible [Fine,K] |
12217 | For ontology we need, not internal or external views, but a view from outside reality [Fine,K] |
12213 | Ontological claims are often universal, and not a matter of existential quantification [Fine,K] |
17371 | Some kinds are very explanatory, but others less so, and some not at all [Devitt] |
17372 | The higher categories are not natural kinds, so the Linnaean hierarchy should be given up [Devitt] |
17373 | Species pluralism says there are several good accounts of what a species is [Devitt] |