Layman's guide to defining evil men

Personality disorder" is, like other functional psychiatric diagnoses, incoherent and contradictory. It adds little to disparate ordinary-language descriptions, which might be subsumed under labels such as "bad", "evil", "weak", "selfish", "feckless", "lacking in conscience", "manipulative" et cetera. These may be pejorative but they are at least honest. As we live within a moral (as well as social and economic) order, these forms of conduct invoke disapproval as well as social control, whether it is in the lay area or in formal political sanctions.

This North American book appears at a time when British politicians are introducing policy revisions about the control and management of "anti-social personality disorder" (ASP). The policy mandate claimed by psychiatrists, such as the author, for their relevant expertise is based on three suppositions. First, that terms such as personality disorder constitute coherent concepts that can be consistently diagnosed when manifested in individuals (reliability). Second, that the disorder has discrete behavioural indices that separate it from other "conditions" (conceptual validity) and the diagnosis predicts outcome (predictive validity). Third, that the cause of the disorder (aetiology) can be specified. In practice, all of these are problematic.

The first point about reliability has been met to some degree. It is hardly surprising that psychiatrists trained to use the same symptom checklist ( DSM-IV or ICD 10 ) will tend to agree on a diagnosis. However, reliability is a necessary but not a sufficient condition for validity. For example, the term "evil" probably enjoys good inter-rater reliability in the general population but its validity is open to question.

With these general problems in mind, a book such as Bad Boys, Bad Men is set to ride for a fall. Donald Black states categorically that ASP is readily separable from criminality (when it is not). He also asserts that it is a biological condition and that violent and ruthless adults cannot be accounted for by childhood abuse or neglect (when the evidence is mixed on both counts). Given that the evidence (biological or environmental) for the causality of anti-social patterns of conduct is highly contested, it is not wise for experts to wade in with such categorical statements about diagnosis and aetiology.

The book's strength is that it is written in a style accessible to the lay person. But given this intention, a more balanced account would have been more cautious, exploring conceptual ambiguity and contested evidence. Moreover, a problem with an individualised approach to violence, evinced in the bio-medical approach favoured by Black, is that it closes off important social questions. Is the hangman, the armed police officer, or the soldier suffering from ASP?

Black would say not. However, the point is that it is not violence per se that is the issue but the social context in which it takes place. As the book demonstrates, biological psychiatrists are not the best social explorers.

David Pilgrim is visiting professor of mental health, University of Liverpool.