This chapter shows explain why Franz Boas maintained that, although statistical analysis of data can shift the burden of proof from one hypothesis to another, even more data must be amassed before a definitive interpretation emerges in most cases. The underlying reason for his empirical fastidiousness is his insight that the causes of human phenomena are more diverse than the phenomena themselves. He shifted the burden of proof onto the stadial view by claiming presumption for the possibility that in the historical sciences similar effects can have different causes. The context in which Boas undermined stadialism and its accompanying racism is important. Boas's rhetorical strategy was apparent when soon after arriving in America he entered into a debate in the pages of Science, the fledgling journal of the American. A short-lived academic post at Clark University, Worchester, Massachusetts, in the eighteen nineties allowed Boas to set up a physical anthropology laboratory.