Final answer:
Humanistic Psychology is sometimes referred to as the third force of psychology because it emphasizes personal control, intentionality, and the belief in a true predisposition for good in our self-concept and behavior.
Step-by-step explanation:
The brand of psychology that was sometimes referred to as the third force of psychology is Humanistic Psychology. Humanism is a perspective within psychology that emphasizes the potential for good that is innate to all humans. It focuses on personal control, intentionality, and the belief in a true predisposition for 'good' as important factors in our self-concept and behavior.