Theorem axin1

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

	Ref	Expression
Assertion	axin1	$$⊢\left(\phi \to \neg \phi \right)\to \neg \phi$$

Proof

Step	Hyp	Ref	Expression
1		pm2.01	$$⊢\left(\phi \to \neg \phi \right)\to \neg \phi$$