Daniel Sennert (1572-1637) was a German physician and Professor of Medicine at the University of Wittenberg. He was a prolific academic author, especially in the field of alchemy or chemistry. Sennert is notable for his contributions to the development of an early version of atomic theory which he set forth in his work, De chymicorum cum Aristotelicis et Galenicis consensu ac dissensu liber: cui accessit appendix de constitutione chymiae (1629). He attempted to reconcile Aristotle with Democritus by arguing that the theory of substantial forms could co-exist with an atomistic understanding of matter: the atoms in gold, for example, retained the substantial form of gold. For Sennert chemistry was an art rather than a science and one which was devoted to two things: "the extraction of essences from natural bodies to be used by physicians and the transmutation of metals". He died of the plague in 1637 at the age of 64.
