Ann believes [Bill left].
Ann believes [Cam left].
-We want an analysis on which all four of these sentences can be true
-simultaneously. If sentences denoted simple truth values or booleans,
-we have a problem: if the sentences *Bill left* and *Cam left* are
-both true, they denote the same object, and Ann's beliefs can't
-distinguish between them.
+We want an analysis on which the first three sentences can be true at
+the same time that the last sentence is false. If sentences denoted
+simple truth values or booleans, we have a problem: if the sentences
+*Bill left* and *Cam left* are both true, they denote the same object,
+and Ann's beliefs can't distinguish between them.
The traditional solution to the problem sketched above is to allow
sentences to denote a function from worlds to truth values, what
thing for a monad unit to do.
Then combining a prediction like *left* which is extensional in its
-subject argument with a monadic subject like `unit ann` is simply bind
+subject argument with an intensional subject like `unit ann` is simply bind
in action:
bind (unit ann) left 1;; (* true: Ann left in world 1 *)