This article examines British Protestant missionary scholars' representations of Tamil culture and history, analysing how this form of knowledge evolved in relation to missionary concerns and the intellectual trends of nineteenth-century India. I focus on the work of Robert Caldwell, whose scholarship had a profound influence on the identity discourses of twentieth-century Tamil nationalism. I situate Caldwell's work in ethnography and philology within the broader field of colonial knowledge produced about Tamils in nineteenth-century India and within a broader study of British missionary concerns in South India. I examine two of Caldwell's publications to argue that his later work, far from being driven by mere scholarly interests, was also shaped by his concerns as a missionary, and that his evolving scholarship mirrored the development of anti-Brahmanism in British Protestant missionary circles of the time. Missionary anti-Brahmanism arose as a response to the caste system, which missionary groups came to regard as the biggest obstacle to Christian conversions. Departing from some of his earlier ideas, Caldwell strategically positioned his later work to challenge Brahman influence, which he saw as being intrinsically tied to the strength of caste sentiment in Indian society. Caldwell's construction of a discursive framework for understanding Tamil linguistic identity was informed by public reactions to his first publication and his subsequent understanding of the dynamic relationship between European scholarship and Indian social relations. More broadly, this article demonstrates the close relationships between Protestant Christian missionary activity, Indian social politics, and the field of knowledge production in colonial South India.