Page "Intensional statement" Paragraph 9

It will be noted that the intensional statements above feature expressions like " knows ", " possible ", and " pleased ".

Such expressions always, or nearly always, produce intensional statements when added ( in some intelligible manner ) to an extensional statement, and thus they ( or more complex expressions like " It is possible that ") are sometimes called intensional operators.

A large class of intensional statements, but by no means all, can be spotted from the fact that they contain intensional operators.