Theorem
pm2.51
Theorem *2.51 of [WhiteheadRussell] p. 107. (Contributed by NM, 3-Jan-2005.)
Conclusion
\( \vdash \neg (\varphi \rightarrow \psi) \rightarrow \varphi \rightarrow \neg \psi \)
Proof
conax1k
This is the content in the right pane.