13 ideas
9193 | ZF set theory has variables which range over sets, 'equals' and 'member', and extensionality [Dummett] |
9194 | The main alternative to ZF is one which includes looser classes as well as sets [Dummett] |
9195 | Intuitionists reject excluded middle, not for a third value, but for possibility of proof [Dummett] |
9186 | First-order logic concerns objects; second-order adds properties, kinds, relations and functions [Dummett] |
9187 | Logical truths and inference are characterized either syntactically or semantically [Dummett] |
9191 | Ordinals seem more basic than cardinals, since we count objects in sequence [Dummett] |
9192 | The number 4 has different positions in the naturals and the wholes, with the same structure [Dummett] |
9086 | The idea of abstract objects is not ontological; it comes from the epistemological idea of abstraction [Plantinga] |
9087 | Theists may see abstract objects as really divine thoughts [Plantinga] |
9085 | If propositions are concrete they don't have to exist, and so they can't be necessary truths [Plantinga] |
9084 | Propositions can't just be in brains, because 'there are no human beings' might be true [Plantinga] |
13304 | Learned men gain more in one day than others do in a lifetime [Posidonius] |
20820 | Time is an interval of motion, or the measure of speed [Posidonius, by Stobaeus] |