Theorem axin2

Description: 'Not' elimination (intuitionistic logic axiom ax-in2). (Contributed by Jim Kingdon, 21-May-2018) (New usage is discouraged.)

	Ref	Expression
Assertion	axin2	$$⊢\neg \phi \to \left(\phi \to \psi \right)$$

Proof

Step	Hyp	Ref	Expression
1		pm2.21	$$⊢\neg \phi \to \left(\phi \to \psi \right)$$