Abstract
The importance of paradigms (models, hypotheses) is emphasized. It is proposed that the reductionist model has dominated the addiction field to the exclusion of existentialist models. The limits of reductionism (typified by the 1980 WHO model of alcohol and other drug use) are explored. Attention is drawn to the characteristics of complex dynamic systems, including their sensitivity to small changes in any factor and the unpredictability of their outcomes. The importance of the capacity of individuals to make choices and the role of chance (both external and internal) is highlighted. The implications for therapy are explored. It is affirmed that therapy is, and will always be, an art, but the technical competence of the therapist can influence effectiveness.