The Authority of Practice in the Alchemy of Sir John Heydon (1588–1653)

Abstract

The social, ideological and personal contours of Lieutenant-General John Heydon’s alchemy provide a case study of how philosophical questions and solutions arise from intertwined practice, theory, and scientific persona. The development of Heydon’s alchemical theory in an unpublished manuscript, A Synopsis of the Universall Entity of Ideas or of ye Systemes of the Maeteriall and Immateriall World, illuminates theories concerning generation and the maintenance of life through aerial nitre theory, which links the early seventeenth-century investigations of Michael Sendivogius and Cornelis Drebbel with later writers such as Kenelm Digby and Robert Boyle. It also provides the context for the early use of thermostatically controlled ovens. Practical concerns within the Ordnance Office could help to explain such interests in saltpetre and efficient ovens. Such practical concerns, however, do not determine the shape that Heydon’s theories took. Rather, theory also shaped Heydon’s notions of practice. Heydon’s particular strand of vitalism granted philosophical authority to experimental practitioners, whether or not they were learned in a traditional sense.