Theorem spfalw 1981

Description: Version of sp 2185 when 𝜑 is false. Uses only Tarski's FOL axiom schemes. (Contributed by NM, 23-Apr-2017.) (Proof shortened by Wolf Lammen, 25-Dec-2017.)

Hypothesis

Ref	Expression
spfalw.1	⊢ ¬ 𝜑

Assertion

Ref	Expression
spfalw	⊢ (∀𝑥𝜑 → 𝜑)

Proof of Theorem spfalw

Step	Hyp	Ref	Expression
1		spfalw.1	. . 3 ⊢ ¬ 𝜑
2	1	hbth 1804	. 2 ⊢ (¬ 𝜑 → ∀𝑥 ¬ 𝜑)
3	2	spnfw 1980	1 ⊢ (∀𝑥𝜑 → 𝜑)

Syntax hints:  ¬ wn 3   → wi 4  ∀wal 1539

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1796  ax-4 1810  ax-6 1968

This theorem depends on definitions:  df-bi 207  df-ex 1781

This theorem is referenced by:  ax6dgen  2130