Since the early sixteenth century, reactions to Theophrastus Philippus Aureolus Bombastus von Hohenheim or Paracelsus have often been as contentious and controversial as the subject himself. Both enfant terrible and revolutionary genius in his formulation of new medical theories and practical cures and procedures, the Swiss-born Paracelsus continued to provoke violent disagreement long after his death in 1541. In addition to medicine and surgery, he received early training in mining, metallurgy, and alchemy; his peripatetic education, like his later career, led him to many locations throughout Europe. Although Paracelsus practiced healing, lectured widely, and wrote voluminously on medical topics, his controversial views and disputatious manner made publication of his ideas rare until after his death. His major contribution to alchemy was its reorientation from gold-making and the pursuit of the philosopher's stone to the formulation and application of medicinal preparations from minerals and chemicals. This shift – combined with his outspoken anti-authoritarianism – necessarily brought him and his followers into conflict with the “official,” academic medical establishment dominated by Galenic physicians and pharmacists who favored herbal medicines (see Allen G. Debus, The English Paracelsians). Paracelsus also wrote in German – not the preferred Latin – and his emphasis on practical experience, experiment, and folk medicine resulted in further alienation.

The following selections from two treatises, Of the Nature of Things and the Aurora (which may be the work of his editor and translator Gerard Dorn), introduce several key Paracelsian ideas, such as the “three-principles theory” (tria prima) of salt, sulphur, and mercury, the making of the homunculus, the generation of metals, the doctrine of signatures, and the role of magic and astrology in his practice of the “Spagyrical Art.”