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\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}