Theorem pm2.43i

Description: Inference absorbing redundant antecedent. Inference associated with pm2.43 . (Contributed by NM, 10-Jan-1993) (Proof shortened by Mel L. O'Cat, 28-Nov-2008)

	Ref	Expression
Hypothesis	pm2.43i.1	$$⊢\phi \to \left(\phi \to \psi \right)$$
Assertion	pm2.43i	$$⊢\phi \to \psi$$

Proof

Step	Hyp	Ref	Expression
1		pm2.43i.1	$$⊢\phi \to \left(\phi \to \psi \right)$$
2		id	$$⊢\phi \to \phi$$
3	2 1	mpd	$$⊢\phi \to \psi$$