There is a central and unavoidable problem at the heart of the work of all health professionals. The practice of medicine and allied professions is increasingly based on empirical science, generating interventions that are essentially technological and standardised. These technologies may be psychological, social or biological (or involve a combination of these modalities). However, the scientific-technological has to be applied in the context of patients' lives, an arena rich in complexity and ambiguity. At its simplest, no matter how effective a drug may be, it cannot work if the patient does not take it. The factors that make patients reluctant to accept advice may appear irrational to clinicians, but they are highly relevant to patients. No one can be expected to accept an intervention unless they are reasonably certain that the balance of the cost–benefit equation will lead to a positive change that is relevant to the quality of their life, as they understand it.

Much of this book is concerned with the development of the fundamental skills of forming and maintaining relationships with patients in order to deploy technologies without causing harm. This first section, however, is about a simultaneous, more technical task: the formation of a diagnostic understanding of the patient's problem, which is based primarily on history taking and mental state examination.

The objective of this section is to understand what one is looking for during assessment, and to explore some of the problems associated with the technical task.