Theorem axin1 2697

Description: 'Not' introduction (intuitionistic logic axiom ax-in1). (Contributed by Jim Kingdon, 21-May-2018.) (New usage is discouraged.)

Assertion

Ref	Expression
axin1	⊢ ((𝜑 → ¬ 𝜑) → ¬ 𝜑)

Proof of Theorem axin1

Step	Hyp	Ref	Expression
1		pm2.01 188	1 ⊢ ((𝜑 → ¬ 𝜑) → ¬ 𝜑)

Syntax hints:  ¬ wn 3   → wi 4

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

This theorem is referenced by: (None)