In the history of medicine as well as in the modern clinical setting, conflicts between two contrastive models of explanation have been observed, the "pathogenic model" and the "recovery model". The pathogenic model focuses on how the pathological process is generated, and has its theoretical background based on the modern mechanistic view of nature. The recovery model focuses on how the recovery process occurs, and has its origin in the ancient Hippocratic school and teleological standpoint. In the context of modern science, the recovery model has always been criticized as a vitalistic and non-rational way of thinking. Some clinicians, however, have reported beneficial effects of certain symptoms. For instance, clinicians may use two different descriptions in the treatment of a fever: 1) the fever should be brought down because it is harmful to the body, or 2) the fever has a beneficial effect on the course of disease. Much research suggests that fever both benefits and harms the body. Therefore, clinical judgments will be based on assessments of these two aspects. Antagonism of the two models is one of the most fundamental themes in the history of medical theory. Hippocrates often referred to the "vis medicatrix naturae" and insisted upon the benefit of symptoms. On the other hand, scientists of the 17th century denied the existence of a "vis medicatrix naturae". To solve this conflict and obtain a basic theory of a model of recovery, we examined the concept of the norm with reference to the philosophy of G. Canguilhem.
