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4. Formal Logic / F. Set Theory ST / 5. Conceptions of Set / f. Limitation of Size

[sets as only limited by vastness that gives problems]

8 ideas
Limitation of Size is not self-evident, and seems too strong [Lavine on Neumann]
     Full Idea: Von Neumann's Limitation of Size axiom is not self-evident, and he himself admitted that it seemed too strong.
     From: comment on John von Neumann (An Axiomatization of Set Theory [1925]) by Shaughan Lavine - Understanding the Infinite VII.1
Limitation of Size is weak (Fs only collect is something the same size does) or strong (fewer Fs than objects) [Boolos, by Potter]
     Full Idea: Weak Limitation of Size: If there are no more Fs than Gs and the Gs form a collection, then Fs form a collection. Strong Limitation of Size: A property F fails to be collectivising iff there are as many Fs as there are objects.
     From: report of George Boolos (Iteration Again [1989]) by Michael Potter - Set Theory and Its Philosophy 13.5
Replacement enforces a 'limitation of size' test for the existence of sets [Bostock]
     Full Idea: The Axiom of Replacement (or the Axiom of Subsets, 'Aussonderung', Fraenkel 1922) in effect enforces the idea that 'limitation of size' is a crucial factor when deciding whether a proposed set or does not not exist.
     From: David Bostock (Philosophy of Mathematics [2009], 5.4)
Limitation of size is part of the very conception of a set [Mayberry]
     Full Idea: Our very notion of a set is that of an extensional plurality limited in size.
     From: John Mayberry (What Required for Foundation for Maths? [1994], p.415-2)
Limitation of Size is a vague intuition that over-large sets may generate paradoxes [Maddy]
     Full Idea: The 'limitation of size' is a vague intuition, based on the idea that being too large may generate the paradoxes.
     From: Penelope Maddy (Believing the Axioms I [1988], §1.3)
     A reaction: This is an intriguing idea to be found right at the centre of what is supposed to be an incredibly rigorous system.
The 'limitation of size' principles say whether properties collectivise depends on the number of objects [Potter]
     Full Idea: We group under the heading 'limitation of size' those principles which classify properties as collectivizing or not according to how many objects there are with the property.
     From: Michael Potter (Set Theory and Its Philosophy [2004], 13.5)
     A reaction: The idea was floated by Cantor, toyed with by Russell (1906), and advocated by von Neumann. The thought is simply that paradoxes start to appear when sets become enormous.
Limitation of Size: if it's the same size as a set, it's a set; it uses Replacement [Lavine]
     Full Idea: Limitation of Size has it that if a collection is the same size as a set, then it is a set. The Axiom of Replacement is characteristic of limitation of size.
     From: Shaughan Lavine (Understanding the Infinite [1994], V.5)
Limitation of Size justifies Replacement, but then has to appropriate Power Set [Hossack]
     Full Idea: The limitation of size conception of sets justifies the axiom of Replacement, but cannot justify Power Set, so NBG set theory appropriates the Power Set axiom from ZFC.
     From: Keith Hossack (Knowledge and the Philosophy of Number [2020], 09.9)
     A reaction: Which suggests that the Power Set axiom is not as indispensable as it at first appears to be.