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Ideas for 'fragments/reports', 'On Note L to Bayle's 'Rorarius'' and 'Necessary Beings'

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5 ideas

5. Theory of Logic / A. Overview of Logic / 7. Second-Order Logic

19296

If second-order variables range over sets, those are just objects; properties and relations aren't sets [Hale]

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]

5. Theory of Logic / C. Ontology of Logic / 4. Logic by Convention

19289

Maybe conventionalism applies to meaning, but not to the truth of propositions expressed [Hale]

5. Theory of Logic / D. Assumptions for Logic / 2. Excluded Middle

6023	Every proposition is either true or false [Chrysippus, by Cicero]

5. Theory of Logic / H. Proof Systems / 4. Natural Deduction

19298

Unlike axiom proofs, natural deduction proofs needn't focus on logical truths and theorems [Hale]