Theorem pm2.45

Description: Theorem *2.45 of WhiteheadRussell p. 106. (Contributed by NM, 3-Jan-2005)

	Ref	Expression
Assertion	pm2.45	$$⊢\neg \left(\phi \vee \psi \right)\to \neg \phi$$

Proof

Step	Hyp	Ref	Expression
1		orc	$$⊢\phi \to \left(\phi \vee \psi \right)$$
2	1	con3i	$$⊢\neg \left(\phi \vee \psi \right)\to \neg \phi$$