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Ideas for 'On What Grounds What', 'Review of Husserl's 'Phil of Arithmetic'' and 'History of Ancient Art'

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7 ideas

6. Mathematics / A. Nature of Mathematics / 4. Using Numbers / e. Counting by correlation
Counting rests on one-one correspondence, of numerals to objects [Frege]
     Full Idea: Counting rests itself on a one-one correlation, namely of numerals 1 to n and the objects.
     From: Gottlob Frege (Review of Husserl's 'Phil of Arithmetic' [1894]), quoted by Richard G. Heck - Cardinality, Counting and Equinumerosity 3
     A reaction: Parsons observes that counting will establish a one-one correspondence, but that doesn't make it the aim of counting, and so Frege hasn't answered Husserl properly. Which of the two is conceptually prior? How do you decide.
Husserl rests sameness of number on one-one correlation, forgetting the correlation with numbers themselves [Frege]
     Full Idea: When Husserl says that sameness of number can be shown by one-one correlation, he forgets that this counting itself rests on a univocal one-one correlation, namely that between the numerals 1 to n and the objects of the set.
     From: Gottlob Frege (Review of Husserl's 'Phil of Arithmetic' [1894], p.326)
     A reaction: This is the platonist talking. Neo-logicism is attempting to build numbers just from the one-one correlation of objects.
6. Mathematics / B. Foundations for Mathematics / 5. Definitions of Number / c. Fregean numbers
In a number-statement, something is predicated of a concept [Frege]
     Full Idea: In a number-statement, something is predicated of a concept.
     From: Gottlob Frege (Review of Husserl's 'Phil of Arithmetic' [1894], p.328)
     A reaction: A succinct statement of Frege's theory of numbers. By my lights that would make numbers at least second-order abstractions.
6. Mathematics / C. Sources of Mathematics / 1. Mathematical Platonism / a. For mathematical platonism
Our concepts recognise existing relations, they don't change them [Frege]
     Full Idea: The bringing of an object under a concept is merely the recognition of a relation which previously already obtained, [but in the abstractionist view] objects are essentially changed by the process, so that objects brought under a concept become similar.
     From: Gottlob Frege (Review of Husserl's 'Phil of Arithmetic' [1894], p.324)
     A reaction: Frege's view would have to account for occasional misapplications of concepts, like taking a dolphin to be a fish, or falsely thinking there is someone in the cellar.
Numbers are not real like the sea, but (crucially) they are still objective [Frege]
     Full Idea: The sea is something real and a number is not; but this does not prevent it from being something objective; and that is the important thing.
     From: Gottlob Frege (Review of Husserl's 'Phil of Arithmetic' [1894], p.337)
     A reaction: This seems a qualification of Frege's platonism. It is why people start talking about abstract items which 'subsist', instead of 'exist'. It shows Frege's motivation in all this, which is to secure logic and maths from the vagaries of psychology.
If 'there are red roses' implies 'there are roses', then 'there are prime numbers' implies 'there are numbers' [Schaffer,J]
     Full Idea: We can automatically infer 'there are roses' from 'there are red roses' (with no shift in the meaning of 'roses'). Likewise one can automatically infer 'there are numbers' from 'there are prime numbers'.
     From: Jonathan Schaffer (On What Grounds What [2009], 2.1)
     A reaction: He similarly observes that the atheist's 'God is a fictional character' implies 'there are fictional characters'. Schaffer is not committing to a strong platonism with his claim - merely that the existence of numbers is hardly worth disputing.
6. Mathematics / C. Sources of Mathematics / 4. Mathematical Empiricism / c. Against mathematical empiricism
The naïve view of number is that it is like a heap of things, or maybe a property of a heap [Frege]
     Full Idea: The most naïve opinion of number is that it is something like a heap in which things are contained. The next most naïve view is the conception of number as the property of a heap, cleansing the objects of their particulars.
     From: Gottlob Frege (Review of Husserl's 'Phil of Arithmetic' [1894], p.323)
     A reaction: A hundred toothbrushes and a hundred sponges can be seen to contain the same number (by one-to-one mapping), without actually knowing what that number is. There is something numerical in the heap, even if the number is absent.