Re: Is {{}} a valid construct?

From: Walt <wamitty_at_verizon.net>
Date: Sun, 18 Feb 2007 22:24:08 GMT
Message-ID: <cm4Ch.1928$2w.342@trndny09>

"Neo" <neo55592_at_hotmail.com> wrote in message news:1170482087.383175.269290_at_k78g2000cwa.googlegroups.com...
> > {} would be the nullary relation called DUM
> > having cardinality and degree zero
> > {{}} would be the nullary relation called DEE
> > having cardinality one and degree zero
> > DEE and DUM are the relational analogs of true and false.
>
> According to my understanding, it seems {} and {{}} are invalid
> constructs. How can I empirically verify they are valid? I can't see
> how nothing means something.
>

What???????

{} is the empty set.
{{}} is the set of sets whose only element is the empty set.

How can they be invalid? Received on Sun Feb 18 2007 - 16:24:08 CST