Theorem 19.36vv 44842

Description: Theorem *11.43 in [WhiteheadRussell] p. 163. Theorem 19.36 of [Margaris] p. 90 with 2 quantifiers. (Contributed by Andrew Salmon, 25-May-2011.)

Assertion

Ref	Expression
19.36vv	⊢ (∃𝑥∃𝑦(𝜑 → 𝜓) ↔ (∀𝑥∀𝑦𝜑 → 𝜓))

Distinct variable groups:   𝜓,𝑥   𝜓,𝑦

Allowed substitution hints:   𝜑(𝑥,𝑦)

Proof of Theorem 19.36vv

Step	Hyp	Ref	Expression
1		19.36v 2001	. . 3 ⊢ (∃𝑦(𝜑 → 𝜓) ↔ (∀𝑦𝜑 → 𝜓))
2	1	exbii 1856	. 2 ⊢ (∃𝑥∃𝑦(𝜑 → 𝜓) ↔ ∃𝑥(∀𝑦𝜑 → 𝜓))
3		19.36v 2001	. 2 ⊢ (∃𝑥(∀𝑦𝜑 → 𝜓) ↔ (∀𝑥∀𝑦𝜑 → 𝜓))
4	2, 3	bitri 277	1 ⊢ (∃𝑥∃𝑦(𝜑 → 𝜓) ↔ (∀𝑥∀𝑦𝜑 → 𝜓))

Syntax hints:   → wi 4   ↔ wb 208  ∀wal 1546  ∃wex 1787

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1803  ax-4 1817  ax-5 1918  ax-6 1975

This theorem depends on definitions:  df-bi 209  df-ex 1788

This theorem is referenced by: (None)