Some problems in the relationship between psychotherapy and scientific research are examined. The following aspects are discussed: the theory of the boundary between science and non-science, the problem of replicability, "hard" and "soft" sciences, complexity and chaos theory, levels of probability and indeterminacy, the inductive-deductive circle, abduction, ecc. Clinical material is presented in order to exemplify the issues under discussion. Some of the problems met by empirical research in psychotherapy (for example the manualization of psychotherapeutic techniques) are described, and certain phases in the history of the psychotherapy research movement are summarized.
Keywords: Science, psychotherapy research, epistemology, replicability, psychoanalytic research, history.