The rational theorists do not know enough about consciousness and rationality to demonstrate to us that the behaviorists are wrong. Thus we are left with a choice. If you accept the rationality of human behavior, then you can use a theory of change based on rational expectations. If you don't, then you cannot use that theory. Such a belief is a critical assumption , one that is necessary for the validity of that theory.
Critical assumptions distinguish one theory from another.
The assumptions you are prepared to accept often determine the theories you are willing to use. The theories you are willing to use also determine the future you expect to occur. If you are a rationalist, then appealing to people's reasonableness will alter the future. If you are a behaviorist, then you will not expect rational appeal alone to change the future. The alternative images of the future that we all hold spring from our assumptions about human nature, the world and the mechanisms of change.