|Geach, Peter T.
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Syntax: Replace salva congruitate: Word chain remains correct when it is replaced. - QuineVs: Replacing changes Syntax: e.g. Copernicus was a complete idiot, iff and only if the earth is a disk. - different ranges: a) Copernicus with predicate + sentence - b) complex predicate - then there is no ambiguous word chain, but different analyzes are possible. - ambiguity: "An astronomer ... iff the earth is flat" can be seen as an operator (like negation). - (Different brackets are possible).
Syntax/Quine/Geach: Quine's 1. Insight: spurious names: problem of range - for real names the problem does not exist. - GeachVsQuine: he, himself blurs the distinction by regarding names as abbreviations of certain descriptions.
3. syntactic insight Quines: E.g. "lx (2x² + 3x³)" - This function of a number: twice its square plus three times its third power - such complex descriptions can be eliminated by usage definition. (Russell):> relative-clause.
4. syntactic insight Quines: Introducing a predicate by a schema letter F. - Problem: E.g.: "Every sentence or its opposite is true" must not become "(Every sentence is true) or ...". - Solution: "F() is then -__ or __s opposite is true". - Geach: sub-clauses (relative-clauses) and pronouns are not mere substitutes. - This is even a mistake in modern logic books.
Logic Matters Oxford 1972