This article examines the English scholar James Cowles Prichard's attention to language and comparative philology within his wider project on the natural history of man. It reveals that linguistic evidence was among the most important elements for Prichard in his overarching scientific aim of investigating human physical diversity, and served as the evidential foundation for his ethnology. His work on Celtic comparative philology made him not only one of the earliest British adopters of German comparative grammar, but a comparative philologist (...) of European stature in his own right. More generally, linguistic evidence helped Prichard to keep his magnum opus, Researches into the Physical History of Mankind, as logically ordered as possible, and therefore to turn ethnology into a discipline with analytical aspirations on a global scale. (shrink)