SYNTAX/SEMANTICS: a predicate which entails or presupposes the truth
of one of its arguments.
EXAMPLE: a sentence such as John knows
that Bill is ill can be true only if its propositional argument
Bill is ill is true. Factive predicates are distinguished from
non-factive predicates (such as believe) and counter-factives (such
as pretend). Thus, the truth-value of John believes that Bill
is ill does not depend on the truth-value of the proposition Bill
is ill, whereas John pretends that he is ill can only be true
if he is not ill.