My main claim in this dissertation, and possibly the most significant contribution that it makes to the field of Romantic studies, is that the prevalent preoccupation with the self and the mind among writers of the Romantic period needs to be evaluated in relation to a rather ancient philosophical and anatomical tradition that goes back to Plato and Galen. The common view among critics that the most influential scientist for the Romantics was Isaac Newton has obscured the extent to which the Romantics were highly responsive to a much earlier, more enduring, and authoritative tradition of anatomical studies. In the first chapter, I examine the significant shift in anatomical literature from Plato's tripartite soul to a single, Christian soul, focusing on Vesalius' monumental contribution to this topic and its representations in the writings of John Donne, Robert Burton, and Christopher Marlowe. Chapter two takes up the political, religious, and literary reactions to Descartes' dualist theory of mind and body, examining the writings of Hobbes, Spinoza, and the Cambridge Platonists in particular. Chapter three considers the debate between vitalism and materialism in the early Romantic period, focusing on John Hunter and John Thelwall, revealing that the distinctions between these categories are not as rigid as has been previously assumed. Chapter four analyzes Samuel Taylor Coleridge's system of esemplastic organicism, tracing its roots in the competing theories of Joseph Priestley, John Abernethy, and William Lawrence. I argue that in spite of its declared allegiance to Christian vitalism, Coleridge embraces a philosophy of materialist evolution that ascribes purposiveness to nature. Chapter five offers an extended study of John Keats, demonstrating that his philosophy of suffering and "Soul-making" is greatly indebted to contemporary medical science, including his own training as a physician. By contextualizing British Romantic literature within the interdisciplinary and transhistorical tradition of anatomical inquiry, I demonstrate that the major shift in anatomy, from searching for the soul to a search for an identity principle – which manifests itself variously as a spark of rational vitality, a metaphysical mind, or a material consciousness – takes place (and could only take place) during the Romantic period.