Theorem orc

Description: Introduction of a disjunct. Theorem *2.2 of WhiteheadRussell p. 104. (Contributed by NM, 30-Aug-1993)

	Ref	Expression
Assertion	orc	$$⊢\phi \to \left(\phi \vee \psi \right)$$

Proof

Step	Hyp	Ref	Expression
1		pm2.24	$$⊢\phi \to \left(\neg \phi \to \psi \right)$$
2	1	orrd	$$⊢\phi \to \left(\phi \vee \psi \right)$$