Theorem pm2.04

Swap antecedents. Theorem *2.04 of [WhiteheadRussell] p. 100. This was the third axiom in Frege's logic system, specifically Proposition 8 of [Frege1879] p. 35. Its associated inference is com12. (Contributed by NM, 27-Dec-1992.) (Proof shortened by Wolf Lammen, 12-Sep-2012.)

Conclusion
\( \vdash (\varphi \rightarrow \psi \rightarrow \chi) \rightarrow \psi \rightarrow \varphi \rightarrow \chi \)
Proof
id
com23 _