Richard Koch first made his appearance in the 1920s with works published on the foundations of medicine. These publications describe the character of medicine as an action and the status of medicine within the theory of science. One of his conclusions is that medicine is not a science in the original sense of the word, but a practical discipline. It serves a practical purpose: to heal the sick. All medical knowledge is oriented towards this purpose, which also defines the physician's role. One kind of knowledge is diagnosis, which is strictly understood in relation to therapy, and is at the core of medical thinking. Diagnosis is not the assignment of a term of a species to a patient's disease: this would not do justice to the individuality of a clinical manifestation and would fail to provide a reason for individual therapy. Nevertheless, the terms assigned to diseases, although fictitious, are not useless, but assist in differentiating various phenomena. These conclusions carry ethical consequences. Because the task of helping the sick constitutes medicine, morals not only set ethical limits: medicine originates in a moral decision. If there are no diseases but only individual sick people, disease can not be defined as an abnormality. The individual benefit to the patient must not necessarily be the complete restoration of health. With its object being incalculable, medicine cannot guarantee its own success. Here the physician has to develop principles that allow for the best possible response to the challenges faced in varying situations of conduct.