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Ideas for 'fragments/reports', 'Difficulties of Transfinite Numbers and Types' and 'Letters to Russell'

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3 ideas

6. Mathematics / C. Sources of Mathematics / 6. Logicism / a. Early logicism
The loss of my Rule V seems to make foundations for arithmetic impossible [Frege]
     Full Idea: With the loss of my Rule V, not only the foundations of arithmetic, but also the sole possible foundations of arithmetic, seem to vanish.
     From: Gottlob Frege (Letters to Russell [1902], 1902.06.22)
     A reaction: Obviously he was stressed, but did he really mean that there could be no foundation for arithmetic, suggesting that the subject might vanish into thin air?
6. Mathematics / C. Sources of Mathematics / 10. Constructivism / d. Predicativism
'Predicative' norms are those which define a class [Russell]
     Full Idea: Norms (containing one variable) which do not define classes I propose to call 'non-predicative'; those which do define classes I shall call 'predicative'.
     From: Bertrand Russell (Difficulties of Transfinite Numbers and Types [1905], p.141)
We need rules for deciding which norms are predicative (unless none of them are) [Russell]
     Full Idea: We need rules for deciding what norms are predicative and what are not, unless we adopt the view (which has much to recommend it) that no norms are predicative. ...[146] A predative propositional function is one which determines a class.
     From: Bertrand Russell (Difficulties of Transfinite Numbers and Types [1905], p.141)
     A reaction: He is referring to his 'no class' theory, which he favoured at that time.