Journal of Medicine and Philosophy, 33: 106–139, 2008 doi:10.1093/jmp/jhn004 © The Author 2008. Published by Oxford University Press, on behalf of the Journal of Medicine and Philosophy Inc. All rights reserved. For permissions, please e-mail: journals.permissions@oxfordjournals.org The Prototype Resemblance Theory of Disease KAZEM SADEGH-ZADEH University of Münster, Münster, Germany In a previous paper the concept of disease was fuzzy-logically ana- lyzed and a sketch was given of a prototype resemblance theory of disease (Sadegh-Zadeh (2000). J. Med. Philos., 25:605–38). This theory is outlined in the present paper. It demonstrates what it means to say that the concept of disease is a nonclassical one and, therefore, not amenable to traditional methods of inquiry. The the- ory undertakes a reconstruction of disease as a category that in contradistinction to traditional views is not based on a set of com- mon features of its members, that is individual diseases, but on a few best examples of the category, called its prototypes, and a similarity relationship such that a human condition is considered a disease if it resembles a prototype. It enables new approaches to resolving many of the stubborn problems associated with the concept of disease. Keywords: classical concepts, concept of disease, family resemblance, nonclassical concepts, prototype resemblance, the prototype resemblance theory of disease I. INTRODUCTION As was argued in a previous paper, the philosophy of disease has reached an impasse and does not progress any more (Sadegh-Zadeh, 2000, 606). This unsatisfactory situation may mainly be attributed to the failure to recognize that there are two types of concepts, classical and nonclassical ones, and that the concept of disease is not a classical one as is traditionally believed, but a nonclassical one and, therefore, requires another approach than is usually taken. In what follows the difference between these two types of concepts is outlined to suggest an adequate method of dealing with the concept of disease. Address correspondence to: Kazem Sadegh-Zadeh, Am Steinkamp 20, Tecklenburg 49545, Germany. E-mail: ksz-2@medizintheorie.de.