Combining Texts

Ideas for 'fragments/reports', 'Truthmakers and Converse Barcan Formula' and 'Causality: Production and Propagation'

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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 / G. Quantification / 1. Quantification
18492 Not all quantification is either objectual or substitutional [Williamson]
     Full Idea: We should not assume that all quantification is either objectual or substitutional.
     From: Timothy Williamson (Truthmakers and Converse Barcan Formula [1999], p.262)
     A reaction: [see Prior 1971:31-4] He talks of quantifying into sentence position.
5. Theory of Logic / G. Quantification / 4. Substitutional Quantification
15136 Substitutional quantification is metaphysical neutral, and equivalent to a disjunction of instances [Williamson]
     Full Idea: If quantification into sentence position is substitutional, then it is metaphysically neutral. A substitutionally interpreted 'existential' quantification is semantically equivalent to the disjunction (possibly infinite) of its substitution instances.
     From: Timothy Williamson (Truthmakers and Converse Barcan Formula [1999], §2)
     A reaction: Is it not committed to the disjunction, just as the objectual reading commits to objects? Something must make the disjunction true. Or is it too verbal to be about reality?
5. Theory of Logic / G. Quantification / 7. Unorthodox Quantification
15138 Not all quantification is objectual or substitutional [Williamson]
     Full Idea: We should not assume that all quantification is objectual or substitutional.
     From: Timothy Williamson (Truthmakers and Converse Barcan Formula [1999], §2)