Other thinkers instead had a pragmatic approach to prime matter: alchemists like the Swiss physician Paracelsus (1493–1541) sought to find a principle to which every substance could be reduced. Though openly challenging traditional university teaching, Paracelsus did not reject canonical motifs. For example, he relied on the four elements (air, fire, water, earth), but he also proposed a new triad: sulfur, mercury, and salt. Yet, even this proposal was not as iconoclastic as it appears, since it was partially founded on the Aristotelian doctrine of the formation of metals contained in the Meteorology (341b 6ff.). Nonetheless, by emphasizing the processes of association and dissociation of substances, Paracelsus offered an important contribution to the transformation of alchemy into chemistry. Gradually chemistry separated from physics, understood as the science of bodies subject to movement, and positioned itself as the science of bodies associated and dissociated. Johann Baptist Van Helmont (1579–1644), who opposed the Paracelsian principles, developed a corpuscular doctrine of matter, a variant of atomistic theory. Atomism in the Renaissance is typically related to the Neoplatonic concept of semina and to the Epicurean philosophy, and was usually advocated by radical anti-Aristotelian thinkers like Giordano Bruno. And while it is true that Aristotle rejected atomism and the existence of the void, there were ways to argue for a Peripatetic version of atomism.