12 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] |
19489 | For me, fictions are internally true, without a significant internal or external truth-value [Yablo] |
19490 | Make-believe can help us to reason about facts and scientific procedures [Yablo] |
19491 | 'The clouds are angry' can only mean '...if one were attributing emotions to clouds' [Yablo] |
5960 | When the soul is intelligent and harmonious, it is part of god and derives from god [Plutarch] |