This paper introduces the notion of plausibility as a decisive condition for the acceptance by groups in society of fundamental ideas concerning the nature of illness.

Plausibility, it is argued, helps to explain both transition from one system of fundamental ideas to another in history, and coexistence of different such systems in a single civilization. Hence this paper challenges an interpretation of medicine prevalent, especially in medical anthropology, since the 1940s, when Erwin Ackerknecht introduced the idea of medicine as an integrated aspect of a society's or community's culture.

Because early research focused on small-scale communities where a majority, if not all, of the members adhered to one world view and experienced one and the same existential environment, medicine came to be identified as a cultural system representative of entire communities and, later, societies. Hence we speak of Chinese medicine as if there were one system of therapeutic ideas and practices representative of China as a whole. The fact is that even though medicine is indeed a cultural system, it is representative only of the culture developed by people sharing identical environments and experiences. That is, if within one civilization different groups coexist in different existential realities entailing different notions of what causes crisis and how to maintain harmony, then these groups will believe in different systems of ideas concerning the generation, treatment, and prevention of illness. Such systems of ideas are therefore always metaphorical reflections of a real social environment or ideas are therefore always metaphorical reflections of a real social environment or of one aspired to.

It is not truth(Wahrheit) that leads to an acceptance of basic therapeutic ideas but plausibility (Wahrschein).