The Swiss physician and alchemist Paracelsus was one of the most influential medical scientists in early modern Europe.

His real name was Theophrastus Aureolus Bombastus von Hohenheim and he was the son of a doctor. After a brief period as a medical student in Italy, he travelled all over Europe and beyond as a military surgeon with the Venetian army, visiting Russia, Arabia and Egypt along the way. Mixing with people from many cultures, he gained considerable knowledge of several folk medicine traditions. ‘I have not been ashamed’, he wrote, ‘to learn from tramps, butchers and barbers.’ These influences led him to reject much of university-taught medicine.

He changed his name to Paracelsus (‘equal to Celsus’) to indicate that he wanted to rival ancient medical authorities such as Galen and Celsus. He rejected Galen’s claim that health and disease were controlled by the four humours and told doctors to study nature and develop personal experience through experiment. On the other hand, he continued to subscribe to all kinds of folk beliefs such as gnomes, spirits and fairies.

Paracelsus also had some training in alchemy, from which he picked up the principle that metals were the key elements which made up the universe, and that they were subject to control by God, the ‘great magician’ who created nature.

Paracelsus argued that the body was a chemical system which had to be balanced not only internally, but which also had to be in harmony with its environment. On the basis of this idea, Paracelsus introduced new chemical substances into medicine, for instance the use of the metal mercury for the treatment of syphilis.

In 1526 he was appointed Professor of Medicine at the University of Basel, Switzerland. Paracelsus overthrew convention by publicly burning the books of Ibn Sina and Galen. He also invited ordinary citizens to his lectures, which he gave wearing an alchemist’s leather apron rather than an academic gown. His new methods were very controversial, and in 1538 he was exiled from Basel. He died in 1541 in Austria.