Thorne, F. C. (1955). Problems of etiology and pathogenicity. In F. C. Thorne, Principals of psychological examining: A systematic textbook of applied integrative psychology (pp. 44-62). Brandon, VT, US: Journal of Clinical Psychology.
http://dx.doi.org/10.1037/13896-003
The principal objective of all diagnosis is, of course, to identify the etiologic factors organizing behavior patterns. Scientifically oriented clinical practice is dedicated to the principle that all physical and psychic phenomena have natural causes which can be clarified by the differentiation of specific cause-effect relationships. Discovering the nature of the problem is always a function of identifying and weighing the factors contributing to the etiologic formula. When this objective can be accomplished, clinical problems are greatly simplified since once we know the nature of the problem its solutions are usually evident. Unfortunately, however, the current status of the science of psychopathology is so undeveloped that available diagnostic methods are frequently unable to identify either the nature of the disorder or specific etiologic factors. In the absence of definitive evidence concerning etiology, it is then necessary to proceed empirically with the process of differential diagnosis. Fortunately, the empirical approach is more efficient than would be expected on logical grounds, since the history of clinical practice is replete with examples where empirical remedies were discovered by chance and used successfully for long periods before their rationale was demonstrated scientifically. On the other hand, many other empirical discoveries have not stood the test of time, so that one must always be critical of clinical practices which are not solidly based on scientific knowledge of etiological relationships. Even though current limitations frequently cause wide discrepancies between theoretical ideals and practical possibilities, the entire diagnostic process should be oriented about the central problem of determining the exact etiology of disorder, or conversely, of the factors which contribute to health. While it is possible to do good clinical work on empirical-intuitive grounds, the clinician never can be absolutely certain of the validity of theory and practice unless specific etiology is demonstrated. The find diagnosis cannot be reached until primary etiologic factors have been identified and this is the fundamental objective of the entire diagnostic process. If primary etiologic factors have been diagnosed, the need for differential diagnosis becomes superfluous since the latter is necessary only when etiologic factors have not been finally clarified. (PsycINFO Database Record (c) 2018 APA, all rights reserved)