How many sick people know that the drugs which are prescribed by their doctors are sometimes totally devoid of active principles? These inactive products - placebos - which have no proven pharmalogical effect are sometimes extremely efficient. Sometimes they are as efficient as classical treatments, or even better since there are no side effects. Should medicine renounce all scientific claims? Some inert substances cure, and authentic medicine have no effect. How is it possible to explain such phenomena? Why do doctors exploit them so little or with such a bad conscience?P. Lemoine, a doctor and psychiatrist specialized in depression, takes us along a fascinating journey into the world of disease and medicine, where we discover strange practices and the unexpected alliance between medicine and magic.