[System method in psychiatry]

The limits of the present methods in psychiatry incite the observer to seek for new methods of investigation. A new method, strictly of operation, can thus be determined from the elements brought in by contemporary epistemology. It's based upon a comparative and differential analysis of the pathologic phenomena gathered in homogeneous groups and sub-groups so as extract from them the permanent functional data (namely the invariants) which are used to constitute open models and systems to be checked by clinical experience. This method is defined here in its terminological and methodological characteristics; its first results and its advantages are pointed out.