Theorem 19.37-1 1697

Description: One direction of Theorem 19.37 of [Margaris] p. 90. The converse holds in classical logic but not, in general, here. (Contributed by Jim Kingdon, 21-Jun-2018.)

Hypothesis

Ref	Expression
19.37-1.1	|- F/ x ph

Assertion

Ref	Expression
19.37-1	|- ( E. x ( ph -> ps ) -> ( ph -> E. x ps ) )

Proof of Theorem 19.37-1

Step	Hyp	Ref	Expression
1		19.37-1.1	. . 3 |- F/ x ph
2	1	19.3 1577	. 2 |- ( A. x ph <-> ph )
3		19.35-1 1647	. 2 |- ( E. x ( ph -> ps ) -> ( A. x ph -> E. x ps ) )
4	2, 3	biimtrrid 153	1 |- ( E. x ( ph -> ps ) -> ( ph -> E. x ps ) )

Syntax hints:   -> wi 4   A.wal 1371   F/wnf 1483   E.wex 1515

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-5 1470  ax-gen 1472  ax-ie1 1516  ax-ie2 1517  ax-4 1533  ax-ial 1557

This theorem depends on definitions:  df-bi 117  df-nf 1484

This theorem is referenced by:  19.37aiv  1698  spcimegft  2851  eqvincg  2897