Robert Boyle is remembered largely for his integration of experiment a
nd the 'mechanical philosophy', Although Boyle is occasionally elusive
as to what he means precisely by the 'mechanical philosophy', it is c
lear that a major portion of it concerned his corpuscular theory of ma
tter. Historians of science have traditionally viewed Boyle's corpuscu
lar philosophy as the grafting of a physical theory onto a previously
incoherent body of alchemy and iatrochemistry. As this essay shows, ho
wever, Boyle owed a heavy debt to a longstanding alchemical theory tha
t postulated the corpuscular make-up of metals and various reagents. I
have elsewhere argued in a general way for Boyle's debt to alchemical
corpuscular theory, but in the present essay I show one of his precis
e sources - namely the Wittenberg medical professor Daniel Sennert (15
72-1637). In his youth Boyle wrote a treatise on corpuscularianism, Of
the Atomicall Philosophy, that borrowed heavily from Sennert without
acknowledgement. Later works, such as The Sceptical Chymist, elaborate
on these borrowings. This discovery shows that we cannot view Boyle's
corpuscular philosophy as an imposition of physics on chemistry: inst
ead, it appears that it originally grew out of chemistry itself. The d
iscovery also throws an interesting light on Boyle's attitude toward s
ources.