Theorem pm10.12

Description: Theorem *10.12 in WhiteheadRussell p. 146. In *10, this is treated as an axiom, and the proofs in *10 are based on this theorem. (Contributed by Andrew Salmon, 17-Jun-2011)

	Ref	Expression
Assertion	pm10.12	|- ( A. x ( ph \/ ps ) -> ( ph \/ A. x ps ) )

Proof

Step	Hyp	Ref	Expression
1		19.32v	|- ( A. x ( ph \/ ps ) <-> ( ph \/ A. x ps ) )
2	1	biimpi	|- ( A. x ( ph \/ ps ) -> ( ph \/ A. x ps ) )