14 ideas
| 13201 | ∈ says the whole set is in the other; ⊆ says the members of the subset are in the other [Enderton] |
| 13206 | A 'linear or total ordering' must be transitive and satisfy trichotomy [Enderton] |
| 13204 | The 'ordered pair' <x,y> is defined to be {{x}, {x,y}} [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] |
| 22200 | If you eliminate the impossible, the truth will remain, even if it is weird [Conan Doyle] |
| 18225 | If we can't reason about value, we can reason about the unconditional source of value [Korsgaard] |
| 18228 | An end can't be an ultimate value just because it is useless! [Korsgaard] |
| 18224 | Goodness is given either by a psychological state, or the attribution of a property [Korsgaard] |
| 18233 | Contemplation is final because it is an activity which is not a process [Korsgaard] |
| 18226 | For Aristotle, contemplation consists purely of understanding [Korsgaard] |