This paper challenges the elite position given to randomised controlled trials (RCTs) in assessing the viability of psychological therapies in the National Health Service. The debate into the significance of the ‘allegiance effect’ in dictating the outcomes of comparative studies into psychological therapies, particularly research that supports behavioural and cognitive behavioural therapies, reconfirms existing methodological arguments that challenge the claims made by traditional scientific methods of research. The underlying epistemological assumptions of RCTs are identified and critiqued with reference to the work of Husserl, Heidegger and Polanyi. An alternative to a scientific approach to research is explored based on Heidegger's theory of Daisen and Polanyi's work on tacit knowledge. The term ‘influence’ is presented as an alternative to the pursuit of causality and the discovery of definitive truth, seen as the underlying motives for a scientific approach to research. From this perspective, the determination of a researcher to persuade others of the value of their particular allegiance to a point of view or orientation could be seen as a potential quality of a study rather than a reason to dismiss the findings. Freud's classic case studies are used to illustrate the epistemological concept of ‘influence’, which represents an understanding of the pursuit of knowledge that is grounded on human experience. The paper concludes by arguing that RCTs should be considered as one of a range of approaches to research that might influence decisions on public funding, seen as part of a more pragmatic approach to research and evidence.