Swiss name: Theophrastus Bombastus von Hohenheim. Swiss physician and alchemist whose work marks the beginning of the emergence of the science of chemistry from alchemy. He was a member of the Hermetic cult, and his works are largely unintelligible. He believed in the "three principles" of Arabian alchemists, consisting of mercury (characterized by fluidity, heaviness, and metallicity), sulfur (characterized by the principle of inflammability), and salt (characterized by the principles of solidity and relative chemical inertness). Nonetheless, he is known as the father of modern pharmacology because of his work in the chemical treatment of medical ailments.

He was closer to the truth than Galen, whose books he burned in public, in ascribing disease to "infectious seeds" (one of the first suggestions that disease was localized) rather than an imbalance in the four humors. He therefore also rejected bloodletting. He rejected previous medical views, believing that "like" cures were required for "like" ailments. Paracelsus concluded that the purpose of alchemy should not be to produce gold, but to concoct medications to treat disease. He was the first to attempt to apply scientific principles towards medicine and was responsible for bringing alchemy and iatrochemistry together into the precursor of modern-day pharmacology. Iatrochemistry was concerned with preparing substances in the simplest way, developing methods to insure consistent results, discovering the medical properties of substances, and finding new substances of medicinal value.

Like Newton, however, his revolutionary contributions to science were accompanied by a seemingly incomprehensible adherence to mystical alchemical research. The Paracelsan philosophy also heavily stressed experimentation. A desire to better understand the human body and treat its ailments led to the practice of experimentation, as physicians tried various treatments to determine which was most effective. Doctors, upon realizing that the existing textbooks were both incorrect and superficial, also began to seek actual hands-on experience through experiment and observation. Paracelsan doctrines were an important part of the impetus behind this movement.

Galen