In Chapter Two, How Psychologists Do Research, we learned that scientists must b

Both psychodynamic and humanist theories are presented in somewhat vague terms that are not operationally defined.
This makes it difficult to develop hypotheses that can be empirically tested. 
Thus, it is not possible to prove or disprove these theories empirically.
With regard to psychodynamic theories, there is the additional problem of repression and the unconscious.
If data become available that would refute psychodynamic theory, theorists resort to saying that the data are either incorrect or incomplete because necessary supporting information has been repressed.
It is difficult but not impossible to empirically test humanist theories so the principle of falsifiability does not apply.  There is not much empirical testing of these theories, but it is conceivably possible to do such research.
It is impossible to empirically test psychodynamic theories, so they are not falsifiable and the theories are not scientific.