14 ideas
10882 | Predicative definitions only refer to entities outside the defined collection [Horsten] |
14249 | Boolos reinterprets second-order logic as plural logic [Boolos, by Oliver/Smiley] |
10830 | Second-order logic metatheory is set-theoretic, and second-order validity has set-theoretic problems [Boolos] |
10829 | A sentence can't be a truth of logic if it asserts the existence of certain sets [Boolos] |
10832 | '∀x x=x' only means 'everything is identical to itself' if the range of 'everything' is fixed [Boolos] |
10884 | A theory is 'categorical' if it has just one model up to isomorphism [Horsten] |
10834 | Weak completeness: if it is valid, it is provable. Strong: it is provable from a set of sentences [Boolos] |
13841 | Why should compactness be definitive of logic? [Boolos, by Hacking] |
10885 | Computer proofs don't provide explanations [Horsten] |
10833 | Many concepts can only be expressed by second-order logic [Boolos] |
10881 | The concept of 'ordinal number' is set-theoretic, not arithmetical [Horsten] |
20949 | Study the use of words, not their origins [Herder] |
7669 | We cannot attain all the ideals of every culture, so there cannot be a perfect life [Herder, by Berlin] |
7668 | Herder invented the idea of being rooted in (or cut off from) a home or a group [Herder, by Berlin] |