Rule of Transposition/Formulation 1/Forward Implication/Proof

Theorem

 * $p \implies q \vdash \neg q \implies \neg p$

Proof

 * align="right" | 3 ||
 * align="right" | 1, 2
 * $\neg p$
 * MTT
 * 1, 2
 * 1, 2