Nothing less than perspicuous demonstration is supposed to put it beyond doubt that a given claim or theory really belongs or amounts to science. When someone 'pretendeth to the science of any thing' and 'only some particular events answer to his pretence', then he is not necessarily a scientist. His pretence to science is not even borne out conclusively when events 'upon many occasions prove so as he says they must ' (E III 37). To qualify as a scientist someone must not only turn out to be right some or most of the time: the basis for his being right has to come out in demonstrations of his claims.