[FOM] Some historical questions

Alasdair Urquhart urquhart at cs.toronto.edu
Sat Nov 6 14:08:53 EDT 2010

"Hartogs' Theorem" usually refers to a result in complex analysis.
The result in set theory is often described as "Hartogs' Lemma".

Hartogs's 6 page paper of 1914 is devoted to a new proof of
the well ordering theorem.  Hartogs deduces the theorem from
the assumption that any two infinite sets are comparable
(there is a bijective mapping from one into a subset of the

You can see the original paper easily online by looking
at the Wikipedia article on "Hartogs number" and clicking
on the link in the list of references.  I haven't studied
the article carefully enough to see just how the lemma
in question is proved in the paper.

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