Abstract:In the face of the “free will-determinism dilemma”, behavioral psychology is confronted with the “explainer’s paradox”: behavioral psychology, as a theoretical framework to explain human psychology and behavior, cannot explain the behavior of the behaviorists themselves. In the theoretical presupposition of behavioral psychology, when human free will is taken away, they are unconsciously endowed with the freedom of their own will. In order to take psychology to further studies, it is necessary to resolve the “explainer’s paradox”. A valid theory of behavioral psychology must effectively explain the behavior of all people, including the explainer himself.