Theorem pm2.67-2

Slight generalization of Theorem *2.67 of [WhiteheadRussell] p. 107. (Contributed by NM, 3-Jan-2005.)

Conclusion

\( \vdash (\varphi \vee \chi \rightarrow \psi) \rightarrow \varphi \rightarrow \psi \)

Proof

orc

imim1i _