[FOM] query about ZFC + (a global choice function)
Aatu.Koskensilta at uta.fi
Sat Dec 18 21:04:31 EST 2010
Quoting Martin Davis <eipye at pacbell.net>:
> I have received an email message inquiring about a rumor that a proof
> had been announced on FOM that:
> ZFC + (a global choice function) is a conservative extension of ZFC.
This follows by a simple forcing argument -- using set sized choice
functions as forcing conditions -- essentially the same way we
establish NBG with global choice is conservative over ZFC. Here I take
ZFC + (a global choice function) is ZFC augmented with a function
symbol posited to choose an element from any non-empty set.
Aatu Koskensilta (aatu.koskensilta at uta.fi)
"Wovon man nicht sprechen kann, darüber muss man schweigen"
- Ludwig Wittgenstein, Tractatus Logico-Philosophicus
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