The studies Of the Celts and of the Indo-Europeans have run parallel with one another since the early 19th century. The modern definition of the Celts is, like that of the Indo-Europeans, purely linguistic, and it is argued in this paper that it is not possible to assign other characteristics such as a distinctive material culture, social organization, or religious practice to either of them without involving unacceptable stereotypical generalizations which are based on outdated ideas based on racist and imperialist concepts.