Medical diagnosis generally requires observed anatomical or physiological abnormalities. Description of the illness and criteria for its diagnosis follow naturally. Recognized symptoms can then be attributed to the observation, and a diagnosis predictably follows. In the case of the functional disorders, such a process is impossible. As there are no observed defects, we only know of the existence of these disorders through the words of our patients. Hence there can be no animal model. Parrots may talk, but are not likely to discuss their bowels. The need to define these disorders of unknown pathology represents a major paradigm shift, a substantial change in thinking for doctors whose training concentrates on basic science and palpable evidence. As more than half of the gut disorders encountered by gastroenterologists and primary care doctors are functional, we must face the reality that scientific evidence to explain these disorders does not exist, and develop alternative . . . [Full text of this article]