of a proposition
about some world or another.

|                  F
|          X o----------&gt;o B
|             \         ^
|              \       /
|             c \     / f
|                \   /
|                 v /
|                  o
|                 B^k
|
|   c(x) = &lt;x_1(x), ..., x_k(x)&gt;

In reading this diagram, one thinks of X as being
a &quot;real world&quot; or an &quot;unknown reality&quot; (UR) and F
as forming a logical proposition about this world,
whose logical values, ranging thro