Theorem bj-con2com

Description: A commuted form of the contrapositive, true in minimal calculus. (Contributed by BJ, 19-Mar-2020)

	Ref	Expression
Assertion	bj-con2com	$$⊢\phi \to \left(\left(\psi \to \neg \phi \right)\to \neg \psi \right)$$

Proof

Step	Hyp	Ref	Expression
1		con2	$$⊢\left(\psi \to \neg \phi \right)\to \left(\phi \to \neg \psi \right)$$
2	1	com12	$$⊢\phi \to \left(\left(\psi \to \neg \phi \right)\to \neg \psi \right)$$