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] |
| 21339 | We want the ontology of relations, not just a formal way of specifying them [Heil] |
| 21349 | Two people are indirectly related by height; the direct relation is internal, between properties [Heil] |
| 21340 | Maybe all the other features of the world can be reduced to relations [Heil] |
| 21348 | In the case of 5 and 6, their relational truthmaker is just the numbers [Heil] |
| 21351 | Truthmaking is a clear example of an internal relation [Heil] |
| 21344 | If R internally relates a and b, and you have a and b, you thereby have R [Heil] |
| 21350 | If properties are powers, then causal relations are internal relations [Heil] |
| 7903 | The six perfections are giving, morality, patience, vigour, meditation, and wisdom [Nagarjuna] |