The heuristics of biologic theory: the case of self-nonself discrimination.

Mel Cohn has responded to our critique of the minimal model of self-nonself discrimination proposed by Langman and him. In this response to Mel Cohn, we summarize the essential differences between our points of view and highlight one criterion (of many) for preferring one theory to another in the complex field of biology: a preferred theory, rather than solving a problem, is heuristic. A good theory is one that activates a scientist to perform experiments that are novel and productive.