Theorem olc

Description: Introduction of a disjunct. Axiom *1.3 of WhiteheadRussell p. 96. (Contributed by NM, 30-Aug-1993)

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

Proof

Step	Hyp	Ref	Expression
1		ax-1	$$⊢\phi \to \left(\neg \psi \to \phi \right)$$
2	1	orrd	$$⊢\phi \to \left(\psi \vee \phi \right)$$