Theorem hbe1 2008

Description: The setvar 𝑥 is not free in ∃𝑥𝜑. (Contributed by NM, 24-Jan-1993.)

Assertion

Ref	Expression
hbe1	⊢ (∃𝑥𝜑 → ∀𝑥∃𝑥𝜑)

Proof of Theorem hbe1

Step	Hyp	Ref	Expression
1		df-ex 1696	. 2 ⊢ (∃𝑥𝜑 ↔ ¬ ∀𝑥 ¬ 𝜑)
2		hbn1 2007	. 2 ⊢ (¬ ∀𝑥 ¬ 𝜑 → ∀𝑥 ¬ ∀𝑥 ¬ 𝜑)
3	1, 2	hbxfrbi 1742	1 ⊢ (∃𝑥𝜑 → ∀𝑥∃𝑥𝜑)

Syntax hints:  ¬ wn 3   → wi 4  ∀wal 1473  ∃wex 1695

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1713  ax-4 1728  ax-10 2006

This theorem depends on definitions:  df-bi 196  df-ex 1696

This theorem is referenced by:  nfe1  2014  nfe1OLD  2020  equs5eALT  2166  equs5e  2337  axie1  2584  wl-dveeq12  32490  ac6s6  33150  exlimexi  37751  vk15.4j  37755  vk15.4jVD  38172