This dissertation charts a lineage of nineteenth-century British literary interventions into the arena of science and philosophy jointly known as vitalism. Intended in part as a contribution to the history of science, Passive Life reconstructs the largely forgotten genealogy of a robust tradition of Victorian-era materialist vitalism, or vital materialism: the theory that a principle of life inheres in all physical matter. I connect this scientific trend to a concurrent surge of cultural engagement with the seventeenth-century philosophy of Baruch Spinoza, whose monist doctrine received renewed attention as experimental developments in biology, physics, physiology, and epidemiology increasingly supported a vital materialist account of the nature of life. Through readings of novels by Mary Shelley, Harriet Martineau, and George Eliot, I position these three women writers as key figures in vitalism’s cultural reception. By attending to the thematic resonances between their novels and materialist vitalism’s major principles and provocations, Passive Life traces the narrative arc of Victorian vitalism, deepening and expanding extant scholarly accounts of the rich interchange among literature and science in the nineteenth century. Moving beyond reception history, however, this dissertation argues that the novels of Shelley, Martineau, and Eliot worked to construct critical interpretations of vitalist theory with a shared emphasis on passivity as a fundamental feature of life. Through innovative techniques of description and characterization, their fiction locates the passivity of life at the level of the material body, in its inherent contingency, fluidity, and impressibility. The view of embodied subjectivity that thus emerges from these novels complicates the liberal humanist model that rose to predominance in Victorian culture and privileged an active, self-determining subject. Within the counter-tradition to which Shelley, Martineau, and Eliot belonged, the idea of “passive life” occasioned pressing ethical and political quandaries involving the relationships between self and other and between subject and environment. On the one hand, treating embodied life as passive pointed speculatively toward more liberated, open-ended, and mutually sustaining forms of communal being. On the other hand, “passive life” also suggested the vulnerability and precarity of bodies helplessly exposed to their material and affective surroundings, raising important questions regarding intention, obligation, and accountability. How do we live well in a world where so many other embodied lives impress upon our own? Can pain and harm be prevented in such a world? What habits of perception and practices of sociality might be evolved and adapted to the realities of passive life? In confronting these questions, nineteenth-century British fiction provides conceptual frameworks well suited to interrogating the political and ethical implications of the twenty-first-century new materialist turn.