Problem #5

Does the Partition Principle imply the Axiom of Choice?

Open!!!Very high impact — resolution would be of award-level significance

The Partition Principle (PP\mathsf{PP}) states that for any sets AA and BB, if there is a surjection from AA to BB then there is an injection from BB to AA. This question asks whether the Partition Principle implies the Axiom of Choice over ZF\mathsf{ZF}.

Known Partial Results

  • Pincus proved that PP\mathsf{PP} implies that every well-ordered family of nonempty sets has a choice function.
  • By a result of Jensen, the above theorem of Pincus shows that PP\mathsf{PP} also implies DC\mathsf{DC}, the Axiom of Dependent Choice.

Notes

This question was first posed in the early 1900s and is one of the oldest open problems in set theory.

Reference for the problem statement

[BM90]Bernhard Banaschewski and Gregory H. Moore, The dual Cantor-Bernstein theorem and the partition principle, Notre Dame Journal of Formal Logic, 1990 [doi]

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