Mental disorder and human nature

Derek Bolton

in What is Mental Disorder?

Published on behalf of Oxford University Press

Published in print February 2008 | ISBN: 9780198565925
Published online February 2013 | e-ISBN: 9780191754401 | DOI:

Series: International Perspectives in Philosophy & Psychiatry

Mental disorder and human nature

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Chapter 3 considers definitions of mental disorder that attempt to clarify the medical, non-social basis for diagnosis in terms of a natural fact – the socalled ‘naturalist’ definitions. Two main naturalist definitions of mental disorder have been proposed, both important and highly influential, one by Christopher Boorse and the other by Jerome Wakefield. Both proposals have mental disorder (and related concepts such as mental or physical illness) as meaning a harmful disruption of natural function. The judgement of harm is taken to be primarily a matter of social norms and values, while the disruption of natural function is claimed to be matter of hard objective, scientific fact. Thus the definitions aim to resolve the 1960s debates by having both social norms and medical norms as components of the concept of mental disorder. Not much is said about the social norms and values involved, because the bulk of the arguments for and against the proposals have been taken up with the second part of the proposed definitions, the vexed issue of what natural function and dysfunction means. This problem goes to the heart of the matter of the justification of the standards by which we distinguish normal from abnormal functioning. Broadly speaking, Boorse and Wakefield between them explore the two available options for distinguishing normal from abnormal functioning in an objective, scientific way.

Boorse seeks to define natural or normal functioning in statistical terms, as average for the species, so that abnormal functioning is a matter of functioning below this species-typical level. There are many problems with this approach. The main one is that deviance from statistical normality in itself – independent of any problems that may result – does not warrant attribution of pathology, physical or mental.Another problem is that statistical abnormality is also relative to specific reference groups, and these can be selected in various ways, delivering different classifications of what is ‘normal’ or ‘abnormal’. Boorse relies on human species-typical functioning to define an absolute gold standard group, which would avoid this relativity, but it is unclear whether there is such a thing. The other approach to defining normal or natural function is to tie it to design, not just to a statistically normal level, and this is the one pursued rigorously by Wakefield. Wakefield links function explicitly to functioning as designed, and thus natural function to functioning as designed in evolution. According to Wakefield's analysis, then, mental disorder is a harmful failure of a natural mental or behavioural mechanism to function as designed in evolution. Wakefield's analysis has much to be said for it, and it may well be the best or the only way of providing an objective, scientific basis for the notion of mental disorder. It has, however, many problems associated with it. One is that diagnosis of mental disorder, according to the analysis, involves a risky hypothesis about causes. There are apparently pathways to conditions of the kind described in the psychiatric manuals that do not involve dysfunction in the sense defined in the analysis, and moreover, it is not generally clear which conditions or presentations do and which do not. The consequence is that it would be impossible to make a definite diagnosis of mental disorder in the clinic, because diagnosis would be conditional on a hypothesis that the presenting problem is or involves failure of an evolutionary designed mechanism to function as designed, a hypothesis that would typically be, for most psychiatric conditions, uncertain, speculative, provisional, for some quite likely false – and in probably all cases controversial. The resulting spectre of unreliability of diagnosis, however, is just the problem – writ large – that the diagnostic manuals have evolved to avoid. In practice, of course, diagnosis in clinical and research settings does not involve evolutionary theoretic speculations, but rather just the diagnostic criteria, which typically appeal to more accessible matters to do with, broadly, breakdown of perceived meaningful connections associated with harm as previously discussed. The implication of this line of thought is that definition of mental disorder in evolutionary theoretic terms, whatever other virtues it may have, does not capture the usage of the term mental disorder in the diagnostic manuals. This requires further consideration of the way the manuals define the conditions of interest, and it opens up terminological problems – both topics deferred to later chapters. It is noted, finally, that the main rationale of the naturalistic definitions of mental disorder, resolution of the 1960s debates about medical vs social norms, is no longer valid, insofar as – as argued in the second chapter – the contrast natural vs social does not survive in the current science.

Chapter.  26781 words. 

Subjects: Psychiatry

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