display all the ideas for this combination of texts
3 ideas
| 13479 | Given that thinking aims at truth, logic gives universal rules for how to do it [Burge] |
| Full Idea: The laws of logic - which are constituted by atemporal thoughts and atemporal subject matter - provide universal prescriptions of how one ought to think, given that one's thinking has the function of attaining truth. | |
| From: Tyler Burge (Frege on Knowing the Third Realm [1992], p.316) | |
| A reaction: Burge is giving, and endorsing, Frege's view. Burge is fighting a rearguard action, when logical systems keep proliferating. See Idea 10282. I sympathise with the dream of Burge and Frege. |
| 8078 | Modus ponens is one of five inference rules identified by the Stoics [Chrysippus, by Devlin] |
| Full Idea: Modus ponens is just one of the five different inference rules identified by the Stoics. | |
| From: report of Chrysippus (fragments/reports [c.240 BCE]) by Keith Devlin - Goodbye Descartes Ch.2 | |
| A reaction: Modus ponens strikes me as being more like a definition of implication than a 'rule'. Implication is what gets you from one truth to another. All the implications of a truth must also be true. |
| 6023 | Every proposition is either true or false [Chrysippus, by Cicero] |
| Full Idea: We hold fast to the position, defended by Chrysippus, that every proposition is either true or false. | |
| From: report of Chrysippus (fragments/reports [c.240 BCE]) by M. Tullius Cicero - On Fate ('De fato') 38 | |
| A reaction: I am intrigued to know exactly how you defend this claim. It may depend what you mean by a proposition. A badly expressed proposition may have indeterminate truth, quite apart from the vague, the undecidable etc. |