3 ideas
14235 | Saying 'they can become a set' is a tautology, because reference to 'they' implies a collection [Cargile] |
18758 | Validity is provable, but invalidity isn't, because the model is infinite [Church, by McGee] |
12887 | A whole must have one characteristic, an internal relation, and a structure [Rescher/Oppenheim] |