\begin{frame} \frametitle{Symmetric Frames: $q \to \all\some q$} We can now make precise why it is impossible to make \begin{align*} q \to \all\some q \end{align*} false on the frame $\F$. \medskip \begin{center} \exampleSymmetric \end{center} \pause \begin{alertblock}{} The reason is that $R$ is \emph{symmetric}: $\myall{x}{\myall{y}{\big(R(x,y) \to R(y,x)\big)}}$ \end{alertblock} \end{frame}