1. This clinical and logical analysis of the concept of schizophrenia is drawn from a statistical work on 366 cases studied for an average of 15 years, with a catamnestic period of 5 years at least.2. As a chronic psychosis, schizophrenia must be separated from acute delusional psychoses.3. As a chronic delusion tending to dissociation of the ego (with breaking of the communications with others and alteration of the reality) schizophrenia is different from the other forms of chronic delusions (paranoia and paraphrenia).4. As a delusion, schizophrenia is different from the neuroses.5. It is only these delimitations that will enable us to define clearly the group of schizophrenias.Abstract Teaser