John Wesley's Primitive Physic (1747) achieved twenty-three editions in his lifetime, ensuring its popular - and controversial - status in eighteenth-century medicine. This is the first full-length study to examine the theological, intellectual and cultural background to one of the period's most successful medical texts. By exploring Wesley's work in the context of his theology, 'A Cheap, Safe and Natural Medicine' extends the on-going reconfiguration of the relationship between religion and medicine. Wesley was on a theological mission to recover the primitive purity of the first Christians. Yet the remedies contained within Primitive Physic suggest a pragmatic thinker, whose concern for spiritual health did not prevent him from providing practical assistance to those who needed it. The evolution of Wesley's thinking also demonstrates some of the struggles he faced as leader of the Methodist movement, such as the way he handled contemporary criticism of Primitive Physic when religious 'enthusiasm' was often conflated with medical 'quackery'. 'A Cheap, Safe and Natural Medicine' will be of interest not only to medical and literary historians, but to anyone who is interested in the way religion influences medicine.