Theorem bj-ex 13718

Description: Existential generalization. (Contributed by BJ, 8-Dec-2019.) Proof modification is discouraged because there are shorter proofs, but using less basic results (like exlimiv 1591 and 19.9ht 1634 or 19.23ht 1490). (Proof modification is discouraged.)

Assertion

Ref	Expression
bj-ex	|- ( E. x ph -> ph )

Distinct variable group:   ph, x

Proof of Theorem bj-ex

Step	Hyp	Ref	Expression
1		ax-ie2 1487	. . 3 |- ( A. x ( ph -> A. x ph ) -> ( A. x ( ph -> ph ) <-> ( E. x ph -> ph ) ) )
2		ax-17 1519	. . 3 |- ( ph -> A. x ph )
3	1, 2	mpg 1444	. 2 |- ( A. x ( ph -> ph ) <-> ( E. x ph -> ph ) )
4		id 19	. 2 |- ( ph -> ph )
5	3, 4	mpgbi 1445	1 |- ( E. x ph -> ph )

Syntax hints:   -> wi 4   <-> wb 104   A.wal 1346   E.wex 1485

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-gen 1442  ax-ie2 1487  ax-17 1519

This theorem depends on definitions:  df-bi 116

This theorem is referenced by:  bj-d0clsepcl  13882  bj-inf2vnlem1  13927  bj-nn0sucALT  13935