Theorem imori

Description: Infer disjunction from implication. (Contributed by NM, 12-Mar-2012)

	Ref	Expression
Hypothesis	imori.1	$$⊢\phi \to \psi$$
Assertion	imori	$$⊢\left(\neg \phi \vee \psi \right)$$

Proof

Step	Hyp	Ref	Expression
1		imori.1	$$⊢\phi \to \psi$$
2		imor	$$⊢\left(\phi \to \psi \right)\leftrightarrow \left(\neg \phi \vee \psi \right)$$
3	1 2	mpbi	$$⊢\left(\neg \phi \vee \psi \right)$$