ABSTRACT In the final chapters of her 1824 Essay upon the Relation of Cause and Effect, Lady Mary Shepherd considers what it means for an organism to be alive. The physician William Lawrence (1783–1867) had recently presented a theory of life that historian Stephen Jacyna has labelled ‘immanentist’. Shepherd’s critique of Lawrence’s arguments reveals a specific application of her own anti-Humean causal theory and shows her own affinities with the ‘transcendentalist’ camp. This paper explores Shepherd’s criticisms of Lawrence, offering some suggestions for understanding Shepherd’s own account of life as a principle, power, or cause, that, when ‘mixed’ with a certain kind of organized body, makes that body living.