  McHugh and Slavney deny that a disease is a physical process—“its essence is conceptual and inferential” (48). This way of thinking about diseases prescinds from theorizing about underlying causes of a disease entity in favor of a concentration on observable phenomena, not hidden causes. However, it is diseases understood as destructive processes that make up the taxa of medicine. Similarly, the successive editions of the DSM have sought to classify mental illnesses based on course and symptoms but not specific causes.