From 1860 until 1977 nurses were inducted into an apprenticeship tradition of care. This tradition, which rested on a vocational ideal of service to humanity as the primary Christian virtue, originated with religious orders and was remodelled and rearticulated by Florence Nightingale to make it acceptable to her contemporary context. This chapter examines Nightingale's principles of nursing, and seeks to understand to what extent they formed the self-understanding of the nursing profession as it developed at St Thomas's Hospital. It presents an analysis that takes account of modern revisionist interpretations which have questioned the influence of Nightingale's training school, her own motives, and the effectiveness of nursing reforms. According to a recent historian of the Nightingale Training School, Roy Wake, Nightingale's work in 'inventing nursing' as a secular and organised profession needs careful scrutiny and modification.