\begin{frame} \frametitle{Propositional Logic: Syntax} \begin{block}{Syntax of Propositional Logic} \begin{itemize} \pause \item propositional variables \begin{talign} p,\; q,\; r,\;\ldots \quad p_0,\;p_1,\;\ldots \end{talign}% \item \pause propositional connectives \begin{talign} \neg,\; \wedge,\; \vee,\; \to \end{talign}% \item \pause propositional formulas \begin{talign} \begin{gathered} p \\ \neg p \\ (\neg p \wedge q) \to r \end{gathered} && \begin{gathered} p \wedge q\\ p \vee \neg q \end{gathered} \end{talign} \end{itemize} \end{block} \pause We use Greek letters for formulas: \begin{align*} \phi &\quad \text{phi} & \psi &\quad \text{psi} & \xi &\quad \text{xi} \\ \alpha &\quad \text{alpha} & \beta &\quad \text{beta} & &\ldots \end{align*} \end{frame}