Theorem pm3.31

Theorem *3.31 (Imp) of [WhiteheadRussell] p. 112. (Contributed by NM, 3-Jan-2005.) (Proof shortened by Wolf Lammen, 24-Mar-2013.)

Conclusion
\( \vdash (\varphi \rightarrow \psi \rightarrow \chi) \rightarrow \varphi \wedge \psi \rightarrow \chi \)
Proof
id
impd _