\begin{frame}
  \begin{block}{Newman's Lemma}
  \smallskip
  SN \& WCR \quad$\Rightarrow$\quad CR\strut
  \end{block}
  
  \bigskip
  
  \begin{definition}<2->[WCR]
  \hspace{-1.5ex}
  \begin{tikzpicture}[on grid,baseline=(1).baseline]
  \node (1)                    {$\strut \alert<3>{a}$};
  \node (2) [below left=of 1]  {$\alert<3>{b}$};
  \node (3) [below right=of 1] {$\alert<3>{c}$};
  \node (4) [below right=of 2] {$\strut d$};
  \node (5) [left=of 1]        {\makebox[3cm][l]{$\strut \forall a,b,c$}};
  \node (6) [left=of 4]        {\makebox[3cm][l]{$\strut \exists d$}};
  \alert<3>{\draw[->] (1) -- (2);}
  \alt<3->{
  \alert<3>{\draw[->] (1) -- (3) node[midway] {\hspace{35mm}peak};}
  }{
  \draw[->] (1) -- (3);
  }
  \draw[dotted,->>] (2) -- (4);
  \draw[dotted,->>] (3) -- (4);
  \end{tikzpicture}
  \end{definition}
  
  \bigskip
  
  \begin{block}<4->{Question}
  \smallskip
  How to prove WCR ?\strut
  \end{block}
\end{frame}