Combining Philosophers

Ideas for Paul Audi, Charles Sanders Peirce and Bob Hale

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2 ideas

5. Theory of Logic / A. Overview of Logic / 3. Value of Logic
Only study logic if you think your own reasoning is deficient [Peirce]
     Full Idea: It is foolish to study logic unless one is persuaded that one's own reasonings are more or less bad.
     From: Charles Sanders Peirce (Criterion of Validity in Reasoning [1903], II)
5. Theory of Logic / A. Overview of Logic / 7. Second-Order Logic
If second-order variables range over sets, those are just objects; properties and relations aren't sets [Hale]
     Full Idea: Contrary to what Quine supposes, it is neither necessary nor desirable to interpret bound higher-order variables as ranging over sets. Sets are a species of object. They should range over entities of a completely different type: properties and relations.
     From: Bob Hale (Necessary Beings [2013], 08.2)
     A reaction: This helpfully clarifies something which was confusing me. If sets are objects, then 'second-order' logic just seems to be the same as first-order logic (rather than being 'set theory in disguise'). I quantify over properties, but deny their existence!