On 09 May 2012, at 13:19, R AM wrote:

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On Wed, May 9, 2012 at 12:48 PM, Bruno Marchal <marc...@ulb.ac.be>wrote:The empty set is the absence of elements (nothing) in that set. Itis the set { }.The empty set is not nothing. For example, the set is { { } } is notempty. It contains as element the empty set.Just to be precise. Well, I guess that the empty set is more like an empty box.

Yes.

`"Nothing", in set theory, would be more like an empty *collection* of`

`sets, or an empty "universe" (a model of set theory), except that in`

`first order logic we forbid empty models (so that AxP(x) -> ExP(x)`

`remains valid, to simplify life (proofs)).`

Bruno http://iridia.ulb.ac.be/~marchal/ -- You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com. To unsubscribe from this group, send email to everything-list+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/everything-list?hl=en.