Theorem stabnot 774

Description: Every formula of the form ¬ 𝜑 is stable. Uses notnotnot 660. (Contributed by David A. Wheeler, 13-Aug-2018.)

Assertion

Ref	Expression
stabnot	⊢ STAB ¬ 𝜑

Proof of Theorem stabnot

Step	Hyp	Ref	Expression
1		notnotnot 660	. . 3 ⊢ (¬ ¬ ¬ 𝜑 ↔ ¬ 𝜑)
2	1	biimpi 118	. 2 ⊢ (¬ ¬ ¬ 𝜑 → ¬ 𝜑)
3		df-stab 773	. 2 ⊢ (STAB ¬ 𝜑 ↔ (¬ ¬ ¬ 𝜑 → ¬ 𝜑))
4	2, 3	mpbir 144	1 ⊢ STAB ¬ 𝜑

Syntax hints:  ¬ wn 3   → wi 4  STAB wstab 772

This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106  ax-in1 576  ax-in2 577

This theorem depends on definitions:  df-bi 115  df-stab 773

This theorem is referenced by: (None)