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Single Idea 9579

[filed under theme 18. Thought / E. Abstraction / 3. Abstracta by Ignoring ]

Full Idea

If from a black cat and a white cat we disregard colour, then posture, then location, ..we finally derive something which is completely without restrictions on content; but what is derived from the objects does differ, although it is not easy to say how.

Gist of Idea

Disregarding properties of two cats still leaves different objects, but what is now the difference?

Source

Gottlob Frege (Review of Husserl's 'Phil of Arithmetic' [1894], p.324)

Book Ref

-: 'Mind July 1972' [-], p.324

A Reaction

This is a key objection to abstractionism for Frege - we are counting two cats, not two substrata of essential catness, or whatever. But what makes a cat countable? (Key question!) It isn't its colour, or posture or location.

The 15 ideas from 'Review of Husserl's 'Phil of Arithmetic''

9821 A definition need not capture the sense of an expression - just get the reference right [Frege, by Dummett]
17446 Counting rests on one-one correspondence, of numerals to objects [Frege]
9577 The naïve view of number is that it is like a heap of things, or maybe a property of a heap [Frege]
9578 If objects are just presentation, we get increasing abstraction by ignoring their properties [Frege]
9580 Our concepts recognise existing relations, they don't change them [Frege]
9579 Disregarding properties of two cats still leaves different objects, but what is now the difference? [Frege]
9581 Many people have the same thought, which is the component, not the private presentation [Frege]
9582 Husserl rests sameness of number on one-one correlation, forgetting the correlation with numbers themselves [Frege]
9583 Psychological logicians are concerned with sense of words, but mathematicians study the reference [Frege]
9584 Identity baffles psychologists, since A and B must be presented differently to identify them [Frege]
9585 Since every definition is an equation, one cannot define equality itself [Frege]
9586 In a number-statement, something is predicated of a concept [Frege]
9587 How do you find the right level of inattention; you eliminate too many or too few characteristics [Frege]
9588 Number-abstraction somehow makes things identical without changing them! [Frege]
9589 Numbers are not real like the sea, but (crucially) they are still objective [Frege]