thm__boolean_algebra_of_subsets.tex

\documentclass{classes/tikzcd}

\begin{document}
  \begin{tikzcd}[every arrow/.append style={dash}]
                    & \set{ A, B }            &                 \\
    \set{ A } \urar &                         & \set{ B } \ular \\
                    & \varnothing \ular \urar &
  \end{tikzcd}
\end{document}