Theorem 19.37-1 1698

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 1578	. 2 |- ( A. x ph <-> ph )
3		19.35-1 1648	. 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 1484   E.wex 1516

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 1471  ax-gen 1473  ax-ie1 1517  ax-ie2 1518  ax-4 1534  ax-ial 1558

This theorem depends on definitions:  df-bi 117  df-nf 1485

This theorem is referenced by:  19.37aiv  1699  spcimegft  2858  eqvincg  2904