B, and has begun to expand
on its further implications.  So let us imagine that the up-looker
has a more deliberate purpose in mind, and that his search for new 
data is driven by the new-found, determinate Rule,

(Rule)   B =&gt; D,   &quot;just Before it rains, Dark clouds appear&quot;.

Contemplating the assumed Case in combination with this new Rule would
lead him by an immediate deduction to predict an additional Fact,

(Fact)   C =&gt; D,   &quot;in the Current situation Dark clouds appear&quot;.

The