16 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] |
10429 | It is best to say that a name designates iff there is something for it to designate [Sainsbury] |
10425 | Definite descriptions may not be referring expressions, since they can fail to refer [Sainsbury] |
10438 | Definite descriptions are usually rigid in subject, but not in predicate, position [Sainsbury] |
10432 | A new usage of a name could arise from a mistaken baptism of nothing [Sainsbury] |
10434 | Even a quantifier like 'someone' can be used referentially [Sainsbury] |
13304 | Learned men gain more in one day than others do in a lifetime [Posidonius] |
10431 | Things are thought to have a function, even when they can't perform them [Sainsbury] |
20820 | Time is an interval of motion, or the measure of speed [Posidonius, by Stobaeus] |