Western academic clinical psychology functions as the primary gateway through which knowledge about psychological suffering becomes legitimized globally. This paper argues that the standards of evidence-based treatment, particularly the criterion of “best available research evidence”, operates not as a neutral scholarly instrument but as a political mechanism that imposes theoretical assumptions onto other frameworks of knowledge. In doing so, it enacts an epistemic colonization that overwrites existing knowledge systems with Western foundations, while simultaneously restricting the emergence and legitimization of new or alternative clinical paradigms. Beneath this seemingly objective standard lies a dense network of theoretical assumptions: epistemological commitments to empiricism, methodological reliance on statistical and experimental hierarchies, and philosophical allegiance to the medical model and materialist conceptions of distress. These assumptions filter out entire forms of clinical theory, rendering alternative frameworks unintelligible or illegitimate. This study will show how these assumptions are embedded in the standard of “best available research,” undermining its pretense of neutrality. We then demonstrate how each imposed assumption has prevented specific current existing paradigms from entering the field, while pressuring others to alter their theoretical foundations to fit in, stripping them of the very novelty that constitutes their value. Finally, we show how this dynamic contributes to the West’s broader global colonization by positioning itself as the sole source of legitimate clinical knowledge, leaving others dependent on its standards and without viable pathways to present their own knowledge on a global stage.