Combining Texts

Ideas for 'The Nature of Things', 'Identity' and 'Letters to Leibniz'

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2 ideas

4. Formal Logic / D. Modal Logic ML / 7. Barcan Formula
No one can conceive of a possible substance, apart from those which God has created [Arnauld]
     Full Idea: I am much mistaken if there is anyone who dares to say that he can conceive of a purely possible substance, …for although one talks so much of them, one never conceives them except according to the notion of those which God has created.
     From: Antoine Arnauld (Letters to Leibniz [1686], 1686.05.13), quoted by David Wiggins - Sameness and Substance 4.2
     A reaction: This idea cashes out in the 'necessitism' of Tim Williamson, and views on the Barcan formulae in modal logic.
4. Formal Logic / F. Set Theory ST / 7. Natural Sets
A class is natural when everybody can spot further members of it [Quinton]
     Full Idea: To say that a class is natural is to say that when some of its members are shown to people they pick out others without hesitation and in agreement.
     From: Anthony Quinton (The Nature of Things [1973], 9 'Nat')
     A reaction: He concedes a number of problems with his view, but I admire his attempt to at least begin to distinguish the natural (real!) classes from the ersatz ones. A mention of causal powers would greatly improve his story.