
Re: Countably Infinite Sets
Posted:
Dec 27, 2012 10:08 PM


On Dec 27, 8:43 pm, netzweltler <reinhard_fisc...@arcor.de> wrote: > Does the set {{1}, {1,2}, {1,2,3}, ...} contain all natural numbers?
No, because it does not contain the natural number 1; if it did, then 1 would be an element of itself, contradiction the axiom of regularity.

