Texts of schizophrenic speakers show significantly more incoherence than those of patients with non-schizophrenic syndromes and normals. In our theory incoherence means a disorder in the implicitly dialogical structure of texts. It is based on deficits in the capacity of taking the role of the other person in social communication. These deficits can be conceived as a common structure of schizophrenic speech disorders and the symptoms of ego-dissociation typically found in schizophrenia. The author supposes, that the deficits in the process of role-taking in social context are caused by fundamental disturbances in self-awareness and self-consciousness of schizophrenics. These disturbances are called Grundverhältnisstörung.