To ensure we offer contemporary continuing education opportunities, the CE credit associated with this video is no longer available, however, the video remains available for viewing.Functional (e.g., Skinnerian) and cognitive approaches in psychology are often seen as competing and mutually exclusive. We argue that although both types of approaches have fundamentally different aims, they are situated at different levels of explanation and can therefore be mutually supportive. More specifically, whereas functional research on the environmental determinants of behavior can help constrain cognitive theories about the mental processes that mediate environment-behavior relations, cognitive research can highlight new empirical phenomena that could help functional researchers to refine behavioral principles and their conceptual or theoretical analyses. We then highlight two implications of our framework for psychotherapy and research on human cognition. First, the framework clarifies the relation between behavior therapy, cognitive behavior therapy, and acceptance and commitment therapy. Second, it sheds new light on the study of rule-governed behavior.