B =&gt; A) and (B =&gt; D).

It is convenient to have the option of expressing all logical statements in terms
of their models, that is, in terms of the primitive circumstances or the elements
of experience over which they hold true.  Let C(-) be a chosen set of experiences,
or the circumstances we have in mind when we refer to &quot;past experience&quot;.  Let C(+)
be a collective set of experiences, or the projective total of possible circumstances.
Let C(0) be a current experience, or the circumstances p