|Quotes: symbols for highlighting parts in a sentence or text. Often for identification of quotations or for distancing. For philosophical problems see also mention/use, quasi-quotation.|
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"It"/Geach: non-referential expression: E.g., the only one who ever stole a book from Snead made a lot of money by selling it - problem: cannot be replaced salva veritate by "Robinson" because then "it" meaningless - in the original also not replaceable by "a book", then also meaningless.
Fake event/Geach: the philosopher, whose student was Plato, was bald - fake: "Plato was bald" - E.g. "A philosopher smoked and drank whiskey": fake: "A philosopher smoked" - "and he (or the philosopher!) drank ... - solution: "casus": two smoking philosophers, one of which does not drink - sentence does not show which is true - but no psychologizing: ("what the speaker thought of" -) what he said is true, even if not all thoughts were true - false question: to what the subject refers to: "he" or "this philosopher" is not a subject at all. - "and" (conjunction) connects here two predicates, not two sentences. - definition fake predicate: if the question is irrelevant to what it is applied to - for example, "everyone loves him- or herself" can be true even if "every man loves ---" does not appeal to anyone. -> anaphora.
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Equivalence/Biconditional/GeachVsBlack: "is material equivalent" is not synonymous with "iff and only if" - "three-dash" ≡ is often read as "material equivalent" - equivalence exists only between sentences, not between names of sentences. - Problem: "Tom loves Mary ↔ Mary loves Tom" is only designating when "↔" (three-dash, ≡) is read as "exactly when" and not as "material equivalent".
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Quotation marks/Geach: E.g. Carnap: If "A" is false, then for every "B" "A > B" is true (quotation marks only on the outside) - This does not contain "B", but "B" directly included in inverted commas -> variables/constants.
Quotation marks/Geach: not a functor that makes the name "Cicero" out of an expression, but an indicator that creates an intentional point of argument into which "Cicero" is inserted. - Thus, iterated quotes have no place in our logic: "name of a name": false - solution: simple symbol, e.g. "tonk" for the name "Cicero" - then e.g. for an x, [Tonk] is a name of [x] and [x] is a proper name. - Quasi-quotation: but is no name.
Logic Matters Oxford 1972