Bob Klahn -> Johnjwilson wrote:

 BK>  John, if someone says "Birds are not flying in this direction",
 BK>  that is not true unless *NO* birds are flying in this
 BK>  direction. Now that is different than saying birds are flying
 BK>  in this direction, which is true if only some birds are flying
 BK>  in this direction.

 BK>  The two important aspects to consider are:

 BK>  A: Saying it isn't happening is not true unless it isn't
 BK>  happening in all relevant instances, but saying it is happening
 BK>  is true even if it's only happening in one case.

And unless you can see that one case you can't prove either statement.

--- Thunderbird 2.0.0.18 (Windows/20081105)