\usepackage{fitch} \usepackage{amsmath} \begin{document} $\Large\begin{nd} \hypo {pq} {P\implies Q} \open \hypo {nq} {\lnot Q} \open \hypo {p} {P} \have {q} {Q} \ie{p,pq} \have {b} {\bot} \ne{q,nq} \close \have {np} {\lnot P} \ii{p-b} \close \have {nqnp} {\lnot Q\implies\lnot P} \ii{nq-np} \end{nd}$ \end{document}