Theorem orri

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

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

Proof

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