What Tom-Ed DID

Tom woke up one morning to find a gold Rolex watch by his bed. It was not the first time valuable objects had appeared in his room. A likeable, easy-going 22 year old, he had come to assume that he was the fortunate, if unlikely recipient of some wealthy benefactor. Later that day he was arrested for robbery with violence. Despite positive identification, he protested his innocence, denying any recollection of the incident. Then, suddenly, he nodded off for a moment, reawakening as a wholly different character. Tom was gone, replaced by Ed, a sullen, hostile, street tough, who readily admitted his successes as a mugger and extortionist.

Tom and Ed, successive selves in Jennifer Radden's terminology, challenge some of our deepest moral and ethical intuitions. Guilt, responsibility, remorse, punishment, law itself, all presuppose "one person one body". Is the amiable Tom responsible for the street-wise Ed's delinquency? Should Tom feel remorse? If we justly punish Ed, should we inflict Ed's punishment on Tom? Will the real Tom-Ed please stand up!

Radden offers no unambiguous answers to such conundra. There is no singular solution to the problem of multiples. But she brings an impressive depth of scholarship to bear - from philosophy, psychiatry, psychology, law and bioethics - in guiding us through this difficult terrain. She is a well-qualified guide. A psychologist as well as philosopher, she is a leading figure in the rapidly expanding field of philosophy and mental health.

Multiple personality disorder has had a chequered history. Depending on whom you talk to, it is clinically commonplace or does not exist. Many psychiatrists, particularly on this side of the Atlantic, consider it no more than an artefact of over-enthusiastic "therapy". Even in the United States, it has had to change its name: in the latest classification is DID, or dissociative identity disorder.

Radden, though, avoids the temptation to circle round this dramatic, if dubious condition. Her route takes in better established disorders of identity in such conditions as dementia, schizophrenia and brain damage. She also examines more everyday phenomena. In Radden's neat phrase, the "theory-wary reader" can dip into her user-friendly book selectively. She has made equally accessible the broad literary themes of liberalism and postmodern identity, and bioethical hot topics, such as involuntary psychiatric treatment, euthanasia and advance directives. Read the book as a whole though, for the twin rewards of a sharp analytic philosopher, cutting through the tangled language of multiples, and an experienced practitioner, showing us a real world of real people.

At the top of Radden's agenda is a reassertion of the individual. Radden deftly counters the many arguments, from philosophy and psychiatry, for a modernist dissolution of the self. Multiples have been widely regarded as showing the constructed nature of personal identity; but as Radden argues, they show only the potential for subdivision. Beware the false inference from the abnormal to the normal case.

Radden also develops a persuasive positive case for retaining a clear notion of distinct persons. Against the challenge of Tom-Ed, she argues, we must acknowledge the "normative tug of individualism". Radden's individuals are defined by relationships; they are socially embedded; and far from their identity being fixed, their successive selves express an essentially open potential for personal change and development. But they are individuals, nonetheless.

This is the first in a series of books on philosophical psychopathology from the MIT Press, edited by the American philosophers, Owen Flanagan and George Graham. After nearly a century of mutual neglect, the series comes on a positive tide of new books on philosophy and psychiatry. There are still those in philosophy, ignorant of the rich variety and subtlety of psychopathology, who think that philosophy can do very well without psychiatry. There are still those in psychiatry, labouring under the "assumption of organicity" (another of Radden's neat phrases), who think that psychiatry can do very well without philosophy. Both are endangered species.

K. W. M. (Bill) Fulford is professor of philosophy and mental health, University of Warwick.