\begin{frame} \frametitle{Modal Formulas} \begin{goal}{Modal Formulas} Modal logic extends propositional logic with \begin{talign} \all && \text{and} && \some \end{talign} as unary (having one argument) connectives. \end{goal} Both $\all$ and $\some$ have the same binding strength as $\neg$. \pause \medskip \begin{exampleblock}{Example formulas} \begin{mgather} \some p \\ \all p \to p \\ \neg \all\neg p \to \some p \\ \some p \wedge \all \neg q \\ \all(p\to q) \wedge \some p \end{mgather} \end{exampleblock} \end{frame}