This chapter considers various methodological issues pertinent to how psychotherapy—including a unified psychotherapeutic approach that is guided by a metatheory—can be systematically studied. It argues that a coherently organized methodological pluralism in psychotherapy research is an essential component of psychotherapy becoming increasingly unified, and suggests integral methodological pluralism (IMP) as a strong candidate for providing such a unified conceptual framework. IMP appears to offer the possibility of becoming what A. W. Staats referred to as a "bridging theory," in which disparate knowledge elements are coherently integrated into a more comprehensive, unified body of knowledge. In order for a research project to be "fully integral," all eight zones and their associated methodologies would need to be implemented, a tall order indeed. However, an appealing aspect of IMP involves its scalability. The "content-free" aspect of the integral model is a key feature because it "provides this unifying framework without the exclusionary processes that place constraints on the ontology of psychotherapy.