CFTR and cystic fibrosis: A previously mentioned example from Simon is that of cystic fibrosis, which is explicitly defined by the essential feature of an abnormal CFTR ion transport system, such that ‘regardless of the reason a patient had problems with the CFTR pump system we would consider him to have cystic fibrosis’ [24, p. 361] and that a person who does not have an abnormal CFTR does not, by definition, have cystic fibrosis.