From Philosopher’s Stone to Phosphorus: Robert Boyle’s Illuminating Experiments

This essay explores Robert Boyle’s efforts to create, and his experimental interactions with, a range of luminous substances—notably phosphorus, which he associated with the philosopher’s stone. For Boyle, phosphorus was alight with spiritual significance, and his investigations into this enigmatic and spectacular substance included elements of pious self-reflection. At the same time, Boyle also acknowledged the possibility that ‘luciferous’ phosphorus had darker, more diabolical origins and uses. The final part of the essay discusses the dynamic relation of secrecy and openness in Boyle’s writings. For Boyle, lucidity is not a just a stylistic but an epistemic quality: it indicates the veracity of a knowledge claim, rather than just being a way of communicating such knowledge. Nonetheless, Boyle also made strategic use of alchemical tropes of secrecy even as he transgressed those conventions in practice, replicating textually the faltering and recursive movement from ignorance to partial understanding that characterised his own experimental practices.