The methodological opposition between the categorical approach and the dimensional approach appears as the main issue for the reorganization of current psychiatric knowledge. After a period exclusively marked by the categorical approach, the dimensional method comes back today complementarily with spectral models, anticipating the development of the future DSM V, scheduled for 2013.

In this abstract, we browse the interaction between these two approaches in the construction of our nosographic from Pinel and Kraepelin to nowadays spectral classifications. Both approaches are compared in an epistemological way, with its pros and cons.

Historical perspective shows how psychiatry begins with categorical classification, which is later replace by dimension taxonomy, since second decade of XX century. Most symptoms are dimensional in nature, and can be transformed into a category by setting a cutoff point. Now, after excessive classification and clinical reductionism applied since DSM III, dimensional approach is emerging to propose a more sensible description about mental disorders. Dimensional approach advantages are a certain facility to explore interpersonal differences without artificial cut-offs, and clinical flexibility. A principal disadvantage is the multiplicity of proposed dimensions, without consensus between different theories. In the other hand, categorical method is familiar to us, and is based on solid clinical empirical data. By the way, clinicians say “the more they know their patients, the more they find it difficult to insert them into a category”, the map is not the territory.

Both approaches must coexist, being each one complementary to each order.