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] |
| 468 | Musical performance can reveal a range of virtues [Damon of Ath.] |
| 7127 | If men are good you should keep promises, but they aren't, so you needn't [Machiavelli] |
| 6309 | The principle foundations of all states are good laws and good armies [Machiavelli] |
| 6306 | People are vengeful, so be generous to them, or destroy them [Machiavelli] |
| 6305 | To retain a conquered state, wipe out the ruling family, and preserve everything else [Machiavelli] |
| 6308 | A sensible conqueror does all his harmful deeds immediately, because people soon forget [Machiavelli] |
| 6307 | A desire to conquer, and men who do it, are always praised, or not blamed [Machiavelli] |
| 7486 | Machiavelli emancipated politics from religion [Machiavelli, by Watson] |