Theorem emptyal 1907

Description: On the empty domain, any universally quantified formula is true. (Contributed by Wolf Lammen, 12-Mar-2023.)

Assertion

Ref	Expression
emptyal	⊢ (¬ ∃𝑥⊤ → ∀𝑥𝜑)

Proof of Theorem emptyal

Step	Hyp	Ref	Expression
1		emptyex 1906	. 2 ⊢ (¬ ∃𝑥⊤ → ¬ ∃𝑥 ¬ 𝜑)
2		alex 1825	. 2 ⊢ (∀𝑥𝜑 ↔ ¬ ∃𝑥 ¬ 𝜑)
3	1, 2	sylibr 234	1 ⊢ (¬ ∃𝑥⊤ → ∀𝑥𝜑)

Syntax hints:  ¬ wn 3   → wi 4  ∀wal 1537  ⊤wtru 1540  ∃wex 1778

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1794  ax-4 1808

This theorem depends on definitions:  df-bi 207  df-tru 1542  df-ex 1779

This theorem is referenced by:  emptynf  1908