      / | \
|                     /  |  \
|                  f /   h   \ g
|                   /    |    \
|                  /     |     \
|                 /      |      \
|                v       v       v
|               o&lt;---p---o---q---&gt;o
|              X       X x Y       Y
|
|
| Thus, given X and Y, &lt;p, q&gt; is &quot;universal&quot; among pairs of
| functions from some set to X and Y, because any other such
| pair &lt;f, g&gt; factors uniquely (via h) through the pair &lt;p, q&gt;.
| This 