Thomas Szasz became famous for being at the vanguard of the anti-psychiatry movement, and his latest book begins ominously enough with the subtitle A Comparative Study of Slavery and Psychiatry. The cover illustration is of a psychotherapist's couch with a ball and chain attached. However, something remarkable has happened in the decades since The Myth of Mental Illness, one of his first polemical attacks on psychiatry, was published (Reference SzaszSzasz, 1962). Szasz now appears to have been transformed into an ally rather than an enemy of the National Health Service general adult psychiatrist. Szasz's project has always been to argue passionately for a boundary of demarcation around the responsibility and power of psychiatry.

For the clinician (generalist) who daily has to cope with an increasing number of referrals for which it seems to have become impossible clearly to indicate what a psychiatrist cannot do or be held responsible for, Szasz is like a lifebelt thrown to a drowning man. After all, he gets to his points quickly and via some catchy slogans: ‘dangerousness is not a disease’, he points out, and this is certainly worth remembering by a society that is increasingly abandoning ‘dangerousness’ at the door of psychiatry.

One of the topical arguments in the book centres on Szasz's favourite preoccupation, coercive psychiatry — topical because of the current controversy over possible new mental health legislation in the UK. Szasz makes the telling point that most often we detain and commit patients not so much because of what they have done in the past, but more because of what they might do in the future — be it to themselves or to others. But the future, philosophy reminds us, is a theoretical construct, and we probably consistently overestimate how much of the future we can reliably determine.

However, if we only ever committed patients after a dangerous event, then psychiatry would be seen to be failing in its science: it is an expertise based on knowledge of human behaviour but how can you claim to know anything if you can predict nothing? Is this not the same charge we level against astrology, which explains everything put predicts nothing? The law operates in precisely the opposite way — you are tried after you have done something reprehensible, not before. It is therefore not surprising that in Szasz's eyes (and in the eyes of many users of mental health services) the whole sectioning process resembles something out of Kafka's The Trial.

As ever, Szasz blames psychiatry for forms of thinking that the rest of society is equally guilty of. All of us — psychiatrists or not — probably could not conduct daily affairs without an overly optimistic sense of a fairly predictable future. Also, Szasz is guilty of some surprisingly weak arguments — one that he marshals in favour of his thesis that psychiatrists cannot predict dangerousness is that if they could, they would not so frequently be the victims of assaults by their own patients.

But what saves this book from being just another mugging of psychiatry is that Szasz does raise a fundamental question at the core of our discipline. If we restricted our attention only to those clients who wanted to see a psychiatrist, and disengaged from all those who really didn't, how different might our professional practice and experience be? Is it not possible that it could be a lot more positive for both clinician and patient? What is useful about this approach is that it would force the rest of society to acknowledge that it is they who desperately want psychiatrists to assist in the management of those who appear unpredictable, suffering and insightless. This is the key point at which Szasz is found wanting. If psychiatry were less eager to take over too many of other people's problems, it might find that it was wooed more. Ironically, then, the great antipsychiatrist could end up saving the profession after all.