 The influence of these ideas on Boas is apparent in his 1887 essay, "The Study of Geography", in which he distinguished between physical science, which seeks to discover the laws governing phenomena, and historical science, which seeks a thorough understanding of phenomena on their own terms.Boas argued that geography is and must be historical in this sense.In 1887, after his Baffin Island expedition, Boas wrote "The Principles of Ethnological Classification", in which he developed this argument in application to anthropology