Vitalism is usually associated with Romantic theories of nature, but the supposition of a 'vital principle' or life-force recurred throughout eighteenth-century natural philosophy, to counter the inadequacy of mechanism to understand the operation of natural life. This book traces the persistent presence of a language of vital nature not only in eighteenth-century science, but in literary and philosophical writing too: in moral philosophy, theories of sensibility and political economy, and in the radical journalism and women's writing of the 1790s. It explores the influence of the Scottish vitalist physiology of Robert Whytt and others on writers and thinkers as diverse as Adam Smith, David Hume, Erasmus Darwin, John Hunter, John Thelwall and Mary Wollstonecraft. In doing so, it shows the centrality of vitalism to eighteenth-century accounts of the body, nature, matter and life, and offers a new way of understanding the relationship between eighteenth-century science and culture and that of the Romantic period.