149/155
\begin{frame}{Reflexivity of Equality}
  We can derive 
  \begin{talign}
    \vdash\; \myall{x}{x = x}
  \end{talign}
  as follows:
  \medskip
  
  \begin{exampleblock}{}
    \begin{tikzpicture}
      \naturaldeduction{
        \namedproofbox{y}{
          \proofstep{$y=y$}{$=_i$};
        }
        \proofstep{$\myall{x}{x=x}$}{$\forall_i\;$ 1--1};
      }
    \end{tikzpicture}
  \end{exampleblock}
\end{frame}