Ideas of Charles Parsons, by Theme

[American, fl. 1980, Professor at Columbia University, then Harvard University.]

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4. Formal Logic / D. Modal Logic ML / 4. Alethic Modal Logic
Modal logic is not an extensional language
     Full Idea: Modal logic is not an extensional language.
     From: Charles Parsons (A Plea for Substitutional Quantification [1971], p.159 n8)
     A reaction: [I record this for investigation. Possible worlds seem to contain objects]
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / j. Axiom of Choice IX
The old problems with the axiom of choice are probably better ascribed to the law of excluded middle
     Full Idea: The difficulties historically attributed to the axiom of choice are probably better ascribed to the law of excluded middle.
     From: Charles Parsons (Review of Tait 'Provenance of Pure Reason' [2009], 2)
     A reaction: The law of excluded middle was a target for the intuitionists, so presumably the debate went off in that direction.
5. Theory of Logic / G. Quantification / 4. Substitutional Quantification
Substitutional existential quantifier may explain the existence of linguistic entities
     Full Idea: I argue (against Quine) that the existential quantifier substitutionally interpreted has a genuine claim to express a concept of existence, which may give the best account of linguistic abstract entities such as propositions, attributes, and classes.
     From: Charles Parsons (A Plea for Substitutional Quantification [1971], p.156)
     A reaction: Intuitively I have my doubts about this, since the whole thing sounds like a verbal and conventional game, rather than anything with a proper ontology. Ruth Marcus and Quine disagree over this one.
On the substitutional interpretation, '(∃x) Fx' is true iff a closed term 't' makes Ft true
     Full Idea: For the substitutional interpretation of quantifiers, a sentence of the form '(∃x) Fx' is true iff there is some closed term 't' of the language such that 'Ft' is true. For the objectual interpretation some object x must exist such that Fx is true.
     From: Charles Parsons (A Plea for Substitutional Quantification [1971], p.156)
     A reaction: How could you decide if it was true for 't' if you didn't know what object 't' referred to?
6. Mathematics / A. Nature of Mathematics / 4. Using Numbers / c. Counting procedure
Parsons says counting is tagging as first, second, third..., and converting the last to a cardinal
     Full Idea: In Parsons's demonstrative model of counting, '1' means the first, and counting says 'the first, the second, the third', where one is supposed to 'tag' each object exactly once, and report how many by converting the last ordinal into a cardinal.
     From: report of Charles Parsons (Frege's Theory of Numbers [1965]) by Richard G. Heck - Cardinality, Counting and Equinumerosity 3
     A reaction: This sounds good. Counting seems to rely on that fact that numbers can be both ordinals and cardinals. You don't 'convert' at the end, though, because all the way you mean 'this cardinality in this order'.
6. Mathematics / C. Sources of Mathematics / 4. Mathematical Empiricism / c. Against mathematical empiricism
General principles can be obvious in mathematics, but bold speculations in empirical science
     Full Idea: The existence of very general principles in mathematics are universally regarded as obvious, where on an empiricist view one would expect them to be bold hypotheses, about which a prudent scientist would maintain reserve.
     From: Charles Parsons (Mathematical Intuition [1980], p.152), quoted by Penelope Maddy - Naturalism in Mathematics
     A reaction: This is mainly aimed at Quine's and Putnam's indispensability (to science) argument about mathematics.
6. Mathematics / C. Sources of Mathematics / 8. Finitism
If functions are transfinite objects, finitists can have no conception of them
     Full Idea: The finitist may have no conception of function, because functions are transfinite objects.
     From: Charles Parsons (Review of Tait 'Provenance of Pure Reason' [2009], 4)
     A reaction: He is offering a view of Tait's. Above my pay scale, but it sounds like a powerful objection to the finitist view. Maybe there is a finitist account of functions that could be given?
7. Existence / D. Theories of Reality / 10. Ontological Commitment / e. Ontological commitment problems
If a mathematical structure is rejected from a physical theory, it retains its mathematical status
     Full Idea: If experience shows that some aspect of the physical world fails to instantiate a certain mathematical structure, one will modify the theory by sustituting a different structure, while the original structure doesn't lose its status as part of mathematics.
     From: Charles Parsons (Review of Tait 'Provenance of Pure Reason' [2009], 2)
     A reaction: This seems to be a beautifully simple and powerful objection to the Quinean idea that mathematics somehow only gets its authority from physics. It looked like a daft view to begin with, of course.