The elaboration of a new concept of the pathogenesis of a familiar but idiopathic disease is always exciting, one way or another. Sometimes, as in the penicillin story, the scientific brotherhood marvels at how the obvious could have escaped it so long. Alternatively, if the new concept is not instantly palatable to all interested parties, the community may be split into adherents and doubters, with strong views on either side. The heat generated by such fission can be an important catalyst of scientific progress: the doubters are upset sufficiently to inspire them to try to disprove the validity of the proposal, while the believers hasten to prove and extend the new concept. This dual process invariably generates new knowledge.