On Jul 6, 9:20 am, MoeBlee <jazzm...@hotmail.com> wrote: > On Jul 2, 6:00 pm, "Ross A. Finlayson" <ross.finlay...@gmail.com> > wrote: > > > Here a choice function is a bijective function from an ordinal (which > > is a collection of all lesser ordinals) to a set, or vice versa. > > What does "here" refer to in your sentence? Choice functions are not > necessarily bijections, nor do they necessarily involve ordinals, so I > don't know what you're talking about. > > MoeBlee
That's a well-ordering. (Also in a theory where the well-ordering principle is axiomatized or a theorem it's an equivalent definition under minimization of terms.) I think the definition of choice function includes that the range contains each element, so it's a surjection onto the set.