This chapter explores historicism in the context of the Victorian language sciences. Initially the influence of Germanic historical and comparative linguistics is discussed, as are the problems human language posed for theories of natural selection. The focus then shifts to prescriptive historicism, and the Icelandic language provides a revealing case-study. Icelandic appeared to have remained unaltered for centuries, utterly impervious to language change, and an ideological yearning for unblemished continuity and purism complicated early Victorian attempts to study the language. Many philologists unquestioning adopted the prescriptive historicism favoured by the noted Danish linguist Rasmus Rask, despite its overt interventionist tendencies. As the nineteenth century progressed, a more descriptive analytical framework emerged, one in which Old Norse and Modern Icelandic were classified as distinct, though historically related, language systems. By the 1880s, the prescriptive historicism of the 1840s had bifurcated into two separate traditions which were both synchronic, rather than diachronic, in emphasis. This complex and compelling development exemplifies some of the ways in which different kinds of historicism were imported, adapted, and sometimes rejected as the language sciences became established as an academic discipline during the Victorian period.