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Ideas for 'fragments/reports', 'Investigations in the Foundations of Set Theory I' and 'Russell's Ontological Development'

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2 ideas

2. Reason / D. Definition / 8. Impredicative Definition
Predicative definitions are acceptable in mathematics if they distinguish objects, rather than creating them? [Zermelo, by Lavine]
     Full Idea: On Zermelo's view, predicative definitions are not only indispensable to mathematics, but they are unobjectionable since they do not create the objects they define, but merely distinguish them from other objects.
     From: report of Ernst Zermelo (Investigations in the Foundations of Set Theory I [1908]) by Shaughan Lavine - Understanding the Infinite V.1
     A reaction: This seems to have an underlying platonism, that there are hitherto undefined 'objects' lying around awaiting the honour of being defined. Hm.
2. Reason / D. Definition / 12. Paraphrase
Russell offered a paraphrase of definite description, to avoid the commitment to objects [Quine]
     Full Idea: Russell's theory involved defining a term not by presenting a direct equivalent of it, but by 'paraphrasis', providing equivalents of the sentences. In this way, reference to fictitious objects can be simulated without our being committed to the objects.
     From: Willard Quine (Russell's Ontological Development [1966], p.75)
     A reaction: I hadn't quite grasped that the modern strategy of paraphrase tracks back to Russell - though it now looks obvious, thanks to Quine. Paraphrase is a beautiful way of sidestepping ontological problems. See Frege on the moons of Jupiter.