Theorem
pm2.67
Theorem *2.67 of [WhiteheadRussell] p. 107. (Contributed by NM, 3-Jan-2005.)
Conclusion
\( \vdash (\varphi \vee \psi \rightarrow \psi) \rightarrow \varphi \rightarrow \psi \)
Proof
pm2.67-2
This is the content in the right pane.