Combining Texts

Ideas for 'Explaining the A Priori', 'Reference and Modality' and 'Introduction to Mathematical Philosophy'

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2 ideas

10. Modality / E. Possible worlds / 1. Possible Worlds / a. Possible worlds
If something is true in all possible worlds then it is logically necessary [Russell]
     Full Idea: Saying that the axiom of reducibility is logically necessary is what would be meant by saying that it is true in all possible worlds.
     From: Bertrand Russell (Introduction to Mathematical Philosophy [1919], XVII)
     A reaction: This striking remark is a nice bridge between Leibniz (about whom Russell wrote a book) and Kripke.
10. Modality / E. Possible worlds / 3. Transworld Objects / a. Transworld identity
We can't quantify in modal contexts, because the modality depends on descriptions, not objects [Quine, by Fine,K]
     Full Idea: 'Necessarily 9>7' may be true while the sentence 'necessarily the number of planets < 7' is false, even though it is obtained by substituting a coreferential term. So quantification in these contexts is unintelligible, without a clear object.
     From: report of Willard Quine (Reference and Modality [1953]) by Kit Fine - Intro to 'Modality and Tense' p. 4
     A reaction: This is Quine's second argument against modality. See Idea 9201 for his first. Fine attempts to refute it. The standard reply seems to be to insist that 9 must therefore be an object, which pushes materialist philosophers into reluctant platonism.