The scientific methodology of psychoanalysis is not identical with that of the so-called 'exact' natural sciences. As to complexity of the observational field, biology is perhaps its nearest neighbour. The interlacing of theoretic basic assumptions with observations must be taken into account. Contrary to, say, the physicist, the psychoanalyst tries at first to grasp the phenomena of his field of work empathically, re-experiences them by identification and then categorizes them rationally. The complicated structure of the psychoanalytic field of observation, the manifold meanings of mental phenomena, imply that any isolation of individual factors such as would be necessary for experimental research, considerably changes the phenomena to be examined. Psychoanalytic research can thus be judged only within the frame of psychoanalytic theory.