>All substances are poison; there is none that is not poison. The right dose differentiates a poison from a remedy. -Parcelsus (1538)
>For physicians who care for patients with cancer daily, Parcelsus was clairvoyant.
This is the opening statement of "Cancer Chemotherapy and Biotherapy." The book was published in 2011 and was written by Bruce A. Chabney and Dan L. Longo.

What strikes me though is that 16th century alchemists are not considered scientists. Even if most of them were quacks, the few who weren't, helped push humanity forward. Why don't they get more credit?