[Jervis and scientific research in psychoterapy: reflections on the problem of plurality of research methods]

It is documented that psychotherapy and its scientific investigation interested Giovanni Jervis since the early 1960s. In this paper an aspect of psychotherapy research that attracted Jervis' interest is discussed. While there is more agreement on the hierarchy among the various methods of outcome research in psychotherapy, it is argued that in the field of process research the discussion on how the many process methods should relate to each other is still open. It is not clear which method is "superior" or "more useful" than others in understanding and measuring behaviour change. This problem is discussed also in its epistemological aspects, e.g., regarding the knowledge of "reality" (the patient's mind) and the eye(glasses) we have (the research methods or "lens" we use). A subdivision of the methods of psychotherapy process research into "thematic" and "structural" methods, used also for the classification of projective tests in personality psychology, is suggested.