Theophrastus von Hohenheim

Theophrastus von Hohenheim (1493–1541 A.D.), called Paracelsus, began to quesiton doctrines handed down from antiquity, demanding knowledge of the active ingredient(s) in prescribed remedies, while rejecting the irrational concoctions and mixtures of medieval medicine.
He prescribed chemically defined substances with such success that professional enemies had him prosecuted as a poisoner. Against such accusations, he defended himself with the thesis
that has become an axiom of pharmacology: “If you want to explain any poison properly,
what then isn‘t a poison? All things are poison, nothing is without poison; the dose alone causes a thing not to be poison.”