title: Horizontal and vertical alignment in tabular cell
body: <p>Most indications I've seen so far seem to indicate that <code>m</code> is used to center cell contents vertically, but it's not working for me. Here's what I have</p>
  
  <pre><code>\begin{table}[htb]
  \centering
  
      \sffamily \begin{tabularx}{1.0\textwidth}{ m{3cm} p{5.5cm} p{5.5cm} }
      \hline
      &amp; 
      \textbf{Helpful}
      &amp;
      \textbf{Harmful}
      \hfill \\ \hline
  
      \textbf{Internal origin} \\ (organization) &amp;
      Item 1
      ~\textbullet~ Item 2
      ~\textbullet~ Item 3
      ~\textbullet~ Item 4
      ~\textbullet~ Item 5
      ~\textbullet~ Item 6
      ~\textbullet~ Item 7
      ~\textbullet~ Item 8
      ~\textbullet~ Item 9
  
      &amp;
      Item 1
      ~\textbullet~ Item 2
      ~\textbullet~ Item 3
      ~\textbullet~ Item 4
      ~\textbullet~ Item 5
      ~\textbullet~ Item 6
      ~\textbullet~ Item 7
      ~\textbullet~ Item 8
      ~\textbullet~ Item 9
  
      \\
      \hline
      \textbf{External origin} \\ (environment) &amp;
      Item 1
      ~\textbullet~ Item 2
      ~\textbullet~ Item 3
      ~\textbullet~ Item 4
      ~\textbullet~ Item 5
      ~\textbullet~ Item 6
      ~\textbullet~ Item 7
      ~\textbullet~ Item 8
      ~\textbullet~ Item 9
  
      &amp;
      Item 1
      ~\textbullet~ Item 2
      ~\textbullet~ Item 3
      ~\textbullet~ Item 4
      ~\textbullet~ Item 5
      ~\textbullet~ Item 6
      ~\textbullet~ Item 7
      ~\textbullet~ Item 8
      ~\textbullet~ Item 9
  
      \\
      \hline
      \end{tabularx} \normalfont
  \caption{SWOT matrix}
  \label{tab:swot-matrix}
  \end{table}
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/iIrWC.png" alt="enter image description here"></p>
  
  <p>I want the left cells to be centred vertically and the top ones horizontally. How can I achieve this?</p>