\begin{frame} \frametitle{Properties of Formulas} \begin{block}{Contingency\mpause[1]{ = sometimes true and sometimes false}} \mpause{ \begin{tgather} p \wedge q \wedge \neg r \end{tgather}}\vspace{-1.5ex} \end{block} \begin{block}{Tautology\mpause{ = always true}} \mpause{ \begin{tgather} p \vee \neg p\\ p \to p\\ ((p \to q) \to p) \to p \end{tgather}}\vspace{-1.5ex} \end{block} \begin{block}{Contradiction\mpause{ = always false}} \mpause{ \begin{tgather} p \wedge \neg p\\ ((p \to q) \to p) \wedge \neg p \end{tgather}}\vspace{-1.5ex} \end{block} \end{frame}