Combining Philosophers

Ideas for Chrysippus, Tertullian and Bernard Linsky

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5 ideas

5. Theory of Logic / B. Logical Consequence / 5. Modus Ponens
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.
5. Theory of Logic / D. Assumptions for Logic / 2. Excluded Middle
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.
5. Theory of Logic / F. Referring in Logic / 2. Descriptions / b. Definite descriptions
18774 Definite descriptions, unlike proper names, have a logical structure [Linsky,B]
     Full Idea: Definite descriptions seem to have a logical structure in a way that proper names do not.
     From: Bernard Linsky (Quantification and Descriptions [2014], 1.1.1)
     A reaction: Thus descriptions have implications which plain names do not.
5. Theory of Logic / F. Referring in Logic / 2. Descriptions / c. Theory of definite descriptions
21727 Definite descriptions theory eliminates the King of France, but not the Queen of England [Linsky,B]
     Full Idea: The theory of definite descriptions may eliminate apparent commitment to such entities as the present King of France, but certainly not to the present Queen of England.
     From: Bernard Linsky (Russell's Metaphysical Logic [1999], 7.3)
5. Theory of Logic / I. Semantics of Logic / 5. Extensionalism
21719 Extensionalism means what is true of a function is true of coextensive functions [Linsky,B]
     Full Idea: With the principle of extensionality anything true of one propositional functions will be true of every coextensive one.
     From: Bernard Linsky (Russell's Metaphysical Logic [1999], 6.3)