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Ideas for 'fragments/reports', 'Papers of 1918' and 'New Essays on Human Understanding'

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6 ideas

5. Theory of Logic / A. Overview of Logic / 3. Value of Logic
12992 Logic teaches us how to order and connect our thoughts [Leibniz]
     Full Idea: Logic teaches us how to order and connect our thoughts.
     From: Gottfried Leibniz (New Essays on Human Understanding [1704], 3.10)
     A reaction: Leibniz had a higher opinion of logic than contemporaries like Locke. The question is whether logic can actually teach us better order than we could otherwise manage, or whether it just describes what most thinkers do.
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 / C. Ontology of Logic / 3. If-Thenism
10056 At bottom eternal truths are all conditional [Leibniz]
     Full Idea: At bottom eternal truths are all conditional, saying 'granted such a thing, such another thing is'.
     From: Gottfried Leibniz (New Essays on Human Understanding [1704], 4.11.14), quoted by Alan Musgrave - Logicism Revisited §4
     A reaction: Thus showing Leibniz to have sympathy with the if-thenist view. He cites geometry as his illustration.
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 / 1. Naming / a. Names
12974 People who can't apply names usually don't understand the thing to which it applies [Leibniz]
     Full Idea: Someone who goes wrong in relating an idea to a name will usually go wrong about the thing he wants the name to stand for.
     From: Gottfried Leibniz (New Essays on Human Understanding [1704], 2.29)
     A reaction: This seems to give tentative support to a Millian account of names, whose only content is just the thing which is named. Leibniz's observation certainly seems to be right.
5. Theory of Logic / K. Features of Logics / 1. Axiomatisation
13002 It is always good to reduce the number of axioms [Leibniz]
     Full Idea: To reduce the number of axioms is always something gained.
     From: Gottfried Leibniz (New Essays on Human Understanding [1704], 4.06)
     A reaction: This is rather revealing about the nature of axioms. They don't have any huge metaphysical status - in fact one might say that their status is epistemological, or even pedagogic. They enable us to get out minds round things.