Theorem pm2.521g2

A general instance of Theorem *2.521 of [WhiteheadRussell] p. 107. (Contributed by NM, 3-Jan-2005.) (Proof shortened by Wolf Lammen, 8-Oct-2012.)

Conclusion

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

Proof

simplim

a1d _