Sennert is notable for his contributions to the development of an early version of atomic theory. Specifically, he forms an intermediate bridge between the works of Geber and the more recognized Corpuscularianists such as Robert Boyle. Corpuscularianism differs from modern atomic theory in a number of significant ways, most noticeably a lack of a mathematical argument for its existence, something Sennert specifically rejected. Sennert is an intermediate step between corpuscular particle theory and Aristotelian forms. The same works that are often sited as demonstrating his early atomist views also emphasize the importance of substantial forms. Sennert's theories were based on an experiential and experimental evidence that he gathered both from eyewitness accounts and his own laboratory experience.