The rationale for this theoretical vacuum is outlined in his 1998 paper[28] and his books Humanizing Madness and Humanizing Psychiatry. Simply put, the purpose of a scientific model is to see if a scientific theory works and to actualize its logical consequences. “In this sense, models are real and their material consequences can be measured, whereas theories are ideas and can no more be measured than daydreams. Model-building separates the theories with a future from those which will always remain dreams.” An example of a true scientific model is longer necked giraffes reach more food, survive at higher rates, and pass on this longer neck trait to their progeny. This is a model (natural selection) of the theory of evolution. Therefore, from an epistemological stance there can be no model of mental disorder without first establishing a theory of the mind. Dr. McLaren does not say that the biopsychosocial model is devoid of merit, just that it does not fit the definition of a scientific model (or theory) and does not “reveal anything that would not be known (implicitly, if not explicitly) to any practitioner of reasonable sensitivity.” He states that the biopsychosocial model should be seen in a historical context as bucking against the trend of biological reductionism which was (and still is) overtaking psychiatry. Engel “has done a very great service to orthodox psychiatry in that he legitimised the concept of talking to people as people.” In short, even though it is correct to say that sociology, psychology, and biology are factors in mental illness, simply stating this obvious fact does not make it a model in the scientific sense of the word.[29][30] [31]

“Some critics point out this question of distinction and of determination of the roles of illness and disease runs against the growing concept of the patient–doctor partnership or patient empowerment, as “biopsychosocial” becomes one more disingenuous euphemism for psychosomatic illness.[20] This may be exploited by medical insurance companies or government welfare departments eager to limit or deny access to medical and social care.[21]

Some psychiatrists see the BPS model as flawed, in either formulation or application. Epstein and colleagues describe six conflicting interpretations of what the model might be, and proposes that “…habits of mind may be the missing link between a biopsychosocial intent and clinical reality.”[22] Psychiatrist Hamid Tavakoli argues that the BPS model should be avoided because it unintentionally promotes an artificial distinction between biology and psychology, and merely causes confusion in psychiatric assessments and training programs, and that ultimately it has not helped the cause of trying to destigmatize mental health.[23]

Sociologist David Pilgrim suggests that a necessary pragmatism and a form of “mutual tolerance” (Goldie, 1977) has forced a co-existence of perspectives, rather than a genuine “theoretical integration as a shared BPS orthodoxy.”[24] Pilgrim goes on to state that despite “scientific and ethical virtues,” the BPS model “…has not been properly realised. It seems to have been pushed into the shadows by a return to medicine and the re-ascendancy of a biomedical model.”[25] However, a vocal philosophical critic of the BPS model, psychiatrist Niall McLaren[26], writes:

“Since the collapse of the 19th century models (psychoanalysis, biologism and behaviourism), psychiatrists have been in search of a model which integrates the psyche and the soma. So keen has been their search that they embraced the so-called ‘biopsychosocial model’ without ever bothering to check its details. If, at any time over the last three decades, they had done so, they would have found it had none. This would have forced them into the embarrassing position of having to acknowledge that modern psychiatry is operating in a theoretical vacuum.”[27]”

http://en.wikipedia.org/wiki/Biopsychosocial_model