Theorem naev

Description: If some set variables can assume different values, then any two distinct set variables cannot always be the same. (Contributed by Wolf Lammen, 10-Aug-2019)

	Ref	Expression
Assertion	naev	|- ( -. A. x x = y -> -. A. u u = v )

Proof

Step	Hyp	Ref	Expression
1		aev	|- ( A. u u = v -> A. x x = y )
2	1	con3i	|- ( -. A. x x = y -> -. A. u u = v )