\begin{frame}
   \frametitle{Kripke Models: Truth in Worlds}

  \begin{goal}{}
    The notation 
    \begin{align*}
      \mathcal{M},w \;\fc\; \phi 
    \end{align*}
    means: formula $\phi$ is true in the world $w$ of Kripke model $\mathcal{M}$.
  \end{goal}
  \bigskip\bigskip
  \pause
  
  We often abbreviate
  \begin{talign}
    \mathcal{M},w \;\fc\; \phi 
  \end{talign}
  as
  \begin{talign}
    w \;\fc\; \phi 
  \end{talign}
  if the Kripke model $\mathcal{M}$ is clear from the context.
\end{frame}