4 ideas
8920 | Equivalence relations are reflexive, symmetric and transitive, and classify similar objects [Lipschutz] |
17813 | Löwenheim-Skolem says any theory with a true interpretation has a model in the natural numbers [White,NP] |
17812 | Finite cardinalities don't need numbers as objects; numerical quantifiers will do [White,NP] |
3061 | Anaxarchus said that he was not even sure that he knew nothing [Anaxarchus, by Diog. Laertius] |