The efforts to define homogenous groups of mental disorders are very similar to the work of a sculptor. The artist usually has to cut small, but also sometimes larger, pieces of wood, marble or clay in an attempt to give the material an identifiable feature. But the material that has been cut continues to exist, not as part of the sculpture, but as material left in the sculptor's workshop.

The history of psychiatry from ancient times to the present is full of the efforts of scientists to create identifiable diagnostic groups (Leibrand and Wettley, 1961; Alexander and Selesnick, 1966; Ackerknecht, 1968; Marneros and Angst, 2000; Angst and Marneros, 2001). But the material of the psychiatric sculptor is not similar to marble or wood, but rather similar to clay. Psychiatrists usually change the form of the diagnosis like the artist the shape of the clay. While the volume remains the same, the shape changes. Even the introduction of longitudinal and prognostic features for defining mental disorders (see p. 16) did not essentially change that reality. A new kind of conceptualisation began only after the pharmacological revolution in the middle of the twentieth century. The introduction of the new pharmacopsychiatry involving antipsychotics, antidepressants and mood stabil-isers did not simply offer new modes of treatment, but also cleared the way for deeper and more fundamental consequences: they were social, ideological, methodological, conceptual, clinical, therapeutic and biological. The diagnosis and classification of mental disorder became more operationalised and standardised than in previous decades.