structure for 'Formal Logic'    |     alphabetical list of themes    |     unexpand these ideas

4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / g. Axiom of Powers VI

[axiom for a new set from any given set]

5 ideas
Power Set: ∀x ∃y ∀z(z ⊂ x → z ∈ y) [Kunen]
     Full Idea: Power Set Axiom: ∀x ∃y ∀z(z ⊂ x → z ∈ y). That is, there is a set y which contains all of the subsets of a given set. Hence we define P(x) = {z : z ⊂ x}.
     From: Kenneth Kunen (Set Theory [1980], §1.10)
The Power Set Axiom is needed for, and supported by, accounts of the continuum [Maddy]
     Full Idea: The Power Set Axiom is indispensable for a set-theoretic account of the continuum, ...and in so far as those attempts are successful, then the power-set principle gains some confirmatory support.
     From: Penelope Maddy (Believing the Axioms I [1988], §1.6)
     A reaction: The continuum is, of course, notoriously problematic. Have we created an extra problem in our attempts at solving the first one?
Powers: All the subsets of a given set form their own new powerset [Clegg]
     Full Idea: Axiom of Powers: For each set there exists a collection of sets that contains amongst its elements all the subsets of the given set.
     From: Brian Clegg (Infinity: Quest to Think the Unthinkable [2003], Ch.15)
     A reaction: Obviously this must include the whole of the base set (i.e. not just 'proper' subsets), otherwise the new set would just be a duplicate of the base set.
The Power Set is just the collection of functions from one collection to another [Lavine]
     Full Idea: The Power Set is just he codification of the fact that the collection of functions from a mathematical collection to a mathematical collection is itself a mathematical collection that can serve as a domain of mathematical study.
     From: Shaughan Lavine (Understanding the Infinite [1994], VI.1)
If the totality of sets is not well-defined, there must be doubt about the Power Set Axiom [Rumfitt]
     Full Idea: Someone who is sympathetic to the thesis that the totality of sets is not well-defined ought to concede that we have no reason to think that the Power Set Axiom is true.
     From: Ian Rumfitt (The Boundary Stones of Thought [2015], 9.6)
     A reaction: The point is that it is only this Axiom which generates the vast and expanding totality. In principle it is hard, though, to see what is intrinsically wrong with the operation of taking the power set of a set. Hence 'limitation of size'?