Paracelsus was a very strange scientist, having both well grounded and mystical beliefs at the same time. Living back in the early 1500's, he contributed much to science that still is used to this day. The maxim "it's the dose that make the poison" is his most well known contribution to modern science, but he was also responsible for giving zinc its name, attempted to use chemicals as medicines and firmly believed that disease was caused by external agents.
But the really goofy stuff is lacking from the Wikipedia page. Paracelsus believed in Sylphs, invisible creatures that lived in the air.  They had a human, feminine form and ...well, there is not point in going on. Thankfully the notion of Sylphs was never taken seriously except by poets and writers of fantasy.
 Sadly, this is still poorly understood by most people. Chemophobia is a result - the fear of chemicals regardless of the quantity. Even more surprisingly, microbiologists overlook the wisdom too. They will endlessly report on e. coli or stapholoccocus or listeria monocytogenes being present, but they never quantify if enough it present to cause illness.
 Then again, maybe he wasn't such a crackpot. 500 years later, we still have people that believe in Sylphs. Paracelsus was trying to establish a scientific world from a non-scientific world. Some people are trying to do the opposite.