f basic propositions is moderately adequate
| to the demands of describing, more or less approximately, every
| other region of a "relatively arbitrary" shape that one needs to
| cover in the universe X, then one finds it basically convenient
| to "factor" any "arbitrary" proposition f : X -&gt; B through the
| "cartesian power space" B^k, as in the following diagram:
|
|                          f
|                    X o------&gt;o B
|                       \     ^
|  c = &lt;x&lt;1&gt;, ..., x&lt;k&gt;&g