Terms such as disorder, illness, disease, dysfunction, and deviance embody the preconceptions of historical development (Klein, 1999). That individuals become ill for no apparent reason, suffering from pain, dizziness, malaise, rash, wasting, etc., has been known since prehistoric days. The recognition of illness led to the social definition of the patient and the development of various treatment institutions (e.g., nursing, medicine, surgery, quacks, and faith healers). Illness is an involuntary affliction that justifies the sick, dependent role (Parsons, 1951). That is, because the sick have involuntarily impaired functioning, it is a reasonable social investment to exempt them (at least temporarily) from normal responsibilities. Illness implies that something has gone wrong. However, gaining exemption from civil or criminal responsibilities is often desired. Therefore, if no objective criteria are available, an illness claim can be viewed skeptically. By affirming involuntary affliction, diagnosis immunizes the patient against charges of exploitative parasitism. Therefore, illness may be considered a hybrid concept, with two components: (1) the necessary inference that something has actually, involuntarily, gone wrong (disease) and (2) the qualification that the result (illness) must be sufficiently major, according to current social values, to ratify the sickness exemption role. The latter component is related to the particular historical stage, cultural traditions, and values. This concept has been exemplified by the phrase ‘‘harmful dysfunction’’ (Wakefield, 1992). However, this does not mean that the illness concept is arbitrary since the inference that something has gone wrong is necessary. Beliefs as to just what has gone wrong (e.g., demon possession, bad air, bacterial infection) as well as the degree of manifested dysfunction that warrants the sick role reflect the somewhat independent levels of scientific and social development (for further reference, see Lewis, 1967). How can we affirm that something has gone wrong if there is no objective evidence? The common statistical definition of abnormality simply is ‘‘unusual.’’ Something is abnormal if it is rare. Although biological variability ensures that someone is at an extreme, there is a strong presumption that something has gone wrong if sufficiently extreme.