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Metamath Proof Explorer

Theorem olc

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

		Ref	Expression
	Assertion	olc	$⊢ φ \to (ψ \lor φ)$

Step	Hyp	Ref	Expression
1		ax-1	$⊢ φ \to (\neg ψ \to φ)$
2	1	orrd	$⊢ φ \to (ψ \lor φ)$