Theorem ori

Description: Infer implication from disjunction. (Contributed by NM, 11-Jun-1994)

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

Proof

Step	Hyp	Ref	Expression
1		ori.1	$$⊢\left(\phi \vee \psi \right)$$
2		df-or	$$⊢\left(\phi \vee \psi \right)\leftrightarrow \left(\neg \phi \to \psi \right)$$
3	1 2	mpbi	$$⊢\neg \phi \to \psi$$