Over the past few decades, scholars have explored the cultivation of scientific identities, the social dimensions of knowledge productionand transmission, and the interplay of literature and scientific discourses. This thesis brings these issues to bear on the work and career of Grant Allen, a prolific late-Victorian author of popular science and fiction, who has been gaining critical attention in the last twenty years. Allen was an important proponent of evolutionary science, particularly as conceptualised by Herbert Spencer, Charles Darwin, and Thomas Huxley. He was widely recognised both for his extensive knowledge of science and his ability to communicate complex notions to general audiences. Yet, his occupation as a popular writer, coupled with a lack of formal training, placed him at the margins of professional science and impeded his serious scientific ambitions. In examining the dialogue between Allen’s non-fiction and popular literature, the thesis both revises current understanding of his role in late-Victorian culture, and in particular his contribution to contemporary debates about scientific identity, forms of knowledge,and the nature of evidence. It asserts his continuing relevance at a time when questions about the public understanding of science have become increasingly urgent.