Theorem bj-ex 15254

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 1609 and 19.9ht 1652 or 19.23ht 1508). (Proof modification is discouraged.)

Assertion

Ref	Expression
bj-ex	⊢ (∃𝑥𝜑 → 𝜑)

Distinct variable group:   𝜑,𝑥

Proof of Theorem bj-ex

Step	Hyp	Ref	Expression
1		ax-ie2 1505	. . 3 ⊢ (∀𝑥(𝜑 → ∀𝑥𝜑) → (∀𝑥(𝜑 → 𝜑) ↔ (∃𝑥𝜑 → 𝜑)))
2		ax-17 1537	. . 3 ⊢ (𝜑 → ∀𝑥𝜑)
3	1, 2	mpg 1462	. 2 ⊢ (∀𝑥(𝜑 → 𝜑) ↔ (∃𝑥𝜑 → 𝜑))
4		id 19	. 2 ⊢ (𝜑 → 𝜑)
5	3, 4	mpgbi 1463	1 ⊢ (∃𝑥𝜑 → 𝜑)

Syntax hints:   → wi 4   ↔ wb 105  ∀wal 1362  ∃wex 1503

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-gen 1460  ax-ie2 1505  ax-17 1537

This theorem depends on definitions:  df-bi 117

This theorem is referenced by:  bj-d0clsepcl  15417  bj-inf2vnlem1  15462  bj-nn0sucALT  15470