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Ideas for 'works', 'fragments/reports' and 'Unpublished Notebooks 1885-86'

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4 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 / C. Ontology of Logic / 1. Ontology of Logic

23196	Logic is a fiction, which invents the view that one thought causes another [Nietzsche]
	Full Idea: The model of a complete fiction is logic. Here a thinking is made up where a thought is posited as the cause of another thought.
	From: Friedrich Nietzsche (Unpublished Notebooks 1885-86 [1886], 34[249])
	A reaction: He could almost be referring to Frege's Third Realm. Most hard core analytic philosophers seem to think that propositions have tight logical relationships which are nothing to do with the people who think them.

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 / E. Structures of Logic / 1. Logical Form

4730	For Aristotle, the subject-predicate structure of Greek reflected a substance-accident structure of reality [Aristotle, by O'Grady]
	Full Idea: Aristotle apparently believed that the subject-predicate structure of Greek reflected the substance-accident nature of reality.
	From: report of Aristotle (works [c.330 BCE]) by Paul O'Grady - Relativism Ch.4
	A reaction: We need not assume that Aristotle is wrong. It is a chicken-and-egg. There is something obvious about subject-predicate language, if one assumes that unified objects are part of nature, and not just conventional.