Theorem 19.3h 1485

Description: A wff may be quantified with a variable not free in it. Theorem 19.3 of [Margaris] p. 89. (Contributed by NM, 5-Aug-1993.) (Revised by NM, 21-May-2007.)

Hypothesis

Ref	Expression
19.3h.1	|- ( ph -> A. x ph )

Assertion

Ref	Expression
19.3h	|- ( A. x ph <-> ph )

Proof of Theorem 19.3h

Step	Hyp	Ref	Expression
1		ax-4 1440	. 2 |- ( A. x ph -> ph )
2		19.3h.1	. 2 |- ( ph -> A. x ph )
3	1, 2	impbii 124	1 |- ( A. x ph <-> ph )

Syntax hints:   -> wi 4   <-> wb 103   A.wal 1282

This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia2 105  ax-ia3 106  ax-4 1440

This theorem depends on definitions:  df-bi 115

This theorem is referenced by:  19.27h  1492  19.28h  1494  equsalh  1654  2eu4  2034