9982
|
Cantor and Dedekind use abstraction to fix grammar and objects, not to carry out proofs [Tait]
|
|
Full Idea:
Although (in Cantor and Dedekind) abstraction does not (as has often been observed) play any role in their proofs, but it does play a role, in that it fixes the grammar, the domain of meaningful propositions, and so determining the objects in the proofs.
|
|
From:
William W. Tait (Frege versus Cantor and Dedekind [1996], V)
|
|
A reaction:
[compressed] This is part of a defence of abstractionism in Cantor and Dedekind (see K.Fine also on the subject). To know the members of a set, or size of a domain, you need to know the process or function which created the set.
|
9985
|
Abstraction may concern the individuation of the set itself, not its elements [Tait]
|
|
Full Idea:
A different reading of abstraction is that it concerns, not the individuating properties of the elements relative to one another, but rather the individuating properties of the set itself, for example the concept of what is its extension.
|
|
From:
William W. Tait (Frege versus Cantor and Dedekind [1996], VIII)
|
|
A reaction:
If the set was 'objects in the room next door', we would not be able to abstract from the objects, but we might get to the idea of things being contain in things, or the concept of an object, or a room. Wrong. That's because they are objects... Hm.
|
9980
|
If abstraction produces power sets, their identity should imply identity of the originals [Tait]
|
|
Full Idea:
If the power |A| is obtained by abstraction from set A, then if A is equipollent to set B, then |A| = |B|. But this does not imply that A = B. So |A| cannot just be A, taken in abstraction, unless that can identify distinct sets, ..or create new objects.
|
|
From:
William W. Tait (Frege versus Cantor and Dedekind [1996], V)
|
|
A reaction:
An elegant piece of argument, which shows rather crucial facts about abstraction. We are then obliged to ask how abstraction can create an object or a set, if the central activity of abstraction is just ignoring certain features.
|