In this paper I consider how alchemists, early modern natural philosophers, contemporary scientists, and the established Church (Roman Catholic and Anglican) express the relationship between such personal character traits as purity and good intent and the efficacy of an individual’s experiments or actions. Both Catholic and Anglican doctrine explicitly state that the efficacy of a sacrament does not depend on the personal attributes of the priest who performs it; this doctrine contrasts with the writings of many early modern alchemists and natural philosophers who argue that the success of an experiment or the efficacy of an action depend at least in part on the personal characteristics of the experimenter or actor. In this respect, the contemporary description of the scientific method is more consistent with the view of the Church than with that of early modern natural philosophers. Similarities between the views of the Church and of the modern scientific establishment appear to arise from similarity in institutional structures, the role of individuals within large and complex organisations, and understanding of the relationship between the individual and the institution; in this respect the established Church and the modern scientific establishment have more in common with each other than with the early modern network of researchers that we traditionally consider the predecessor of the modern scientific establishment. A consideration of these differing views of the effect of personal traits on experimental efficacy can help us develop a better understanding of how we have come to differentiate between ‘arts’ and ‘sciences’, the distinctive nature of craft knowledge, and the relationship between employer and employee in capitalist economies.