On 4/5/2013 3:52 PM, WM wrote: > On 5 Apr., 22:06, fom <fomJ...@nyms.net> wrote: >> On 4/5/2013 11:22 AM, WM wrote: >> >>> On 5 Apr., 12:08, William Hughes <wpihug...@gmail.com> wrote: >> >>>> More precisely. There is an infinite set of lines D >>>> such that any finite subset of D can be removed. >> >>> How do you call a subset of D that has no fixed last element? >> >> In set theory it is neither a set or a subset > > In set theory a set can either be bijected with a FISON or not. >
That is in set theory. You do no mathematics according to the axioms or logic of set theory.
Sets are fixed objects by virtue of the identity criterion associated with the system of representation.
There is never "a subset of D that has no fixed last element".
You may compare your remark to the "round square" as a self-contradicting, non-instantiable, use of description.