From araizen@newmail.net Thu Nov 07 08:30:55 2002
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Date: Thu, 07 Nov 2002 16:30:53 -0000
To: lojban@yahoogroups.com
Subject: Re: importing ro
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From: "Adam Raizen" <araizen@newmail.net>
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la .and. cusku di'e

> 2. The universe is not empty.

I don't accept this unless you add it as an axiom to your system. Note
(from
http://www.cgl.uwaterloo.ca/~wbcowan/teaching/cs24
6/s97/notes/lect07.html):

"Instantiation: ForAll x: Px => There exists x: Px as long as the
universe is not empty."

and 

"Note the important role played by the empty universe. (ForAll x:
Fx is true for any F if the universe is empty.)"

So it's not obvious that the *only* possibility in logic is that AxFx
-> ExFx on its own, without the additional postulate of a non-empty
universe.

mu'o mi'e .adam.