Here, Irun Cohen argues that the clonal selection paradigm is no longer a convenient paradigm for organizing thinking about the immune system. He contends that most immunologists now investigate questions for which the clonal selection paradigm makes no provision and that one of its major tenets is contradicted by the prevalence of natural autoimmunity. Instead, he proposes a cognitive paradigm.

Mental paradigms are models that simplify complexity, ideas that help to make sense out of the infinitely complex continuum which is reality. No idea can represent reality as it is. A paradigm merely represents a fragment of reality in a way that allows the mind to deal with it: it encodes a part of the world to the mind's specifications. A paradigm is formed and retained because it is useful, not because it is reaP. A scientific paradigm marks out a conceptual territory for exploration by observation and experimentation. It establishes a world view that defines which questions are worth studying and what answers might be expected. Thus, the prevailing paradigm will bias the way the scientist views and interprets the results of experiment. Certainly, the prevailing paradigm can determine the experiment's publishability. Paradigms must be taken seriously: they influence what we see and what we say. An antiquated paradigm is a hazard. The paradigm which, for over three decades, has organized immunological thinking is clonal selection-'. The clonal selection paradigm holds the antigens responsible for organizing the immune system; only those lymphocyte clones bearing receptors that match the antigens encountered by the individual flourish. To avoid autoimmunity, recognition of self is forbidden. Thus does the clonal selection paradigm explain the specificity of adaptive immunity and the tolerance for antigens of the self. The world view inculcated by the clonal selection paradigm has led many immunologists to believe that the primary function of the immune system is to distinguish between the self and the foreign. A textbook by Jan Klein embodies this belief in its