Implications

We have the following indirect implication of form equivalence classes:

231 \(\Rightarrow\) 38
given by the following sequence of implications, with a reference to its direct proof:

Implication Reference
231 \(\Rightarrow\) 32 clear
32 \(\Rightarrow\) 5 clear
5 \(\Rightarrow\) 38 Non-constructive properties of the real numbers, Howard, P. 2001, Math. Logic Quart.

Here are the links and statements of the form equivalence classes referenced above:

Howard-Rubin Number Statement
231:

\(UT(WO,WO,WO)\): The union of a well ordered collection of well orderable sets is well orderable.

32:

\(C(\aleph_0,\le\aleph_0)\): Every denumerable set of non-empty countable sets  has a choice function.

5:

\(C(\aleph_0,\aleph_0,\Bbb R)\): Every denumerable set of non-empty denumerable subsets of \({\Bbb R}\) has a choice function.

38:

\({\Bbb R}\) is not the union of a countable family of countable sets.

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