Paracelsus is the professional name of Theophrastus Phillippus Aureolus Bombastus von Hohenheim (1493–1531), a German alchemist, physician, and occultist. The professional name was a reference back in time to the Roman physician Celsus (ca. 25 BCE–50 CE). He adopted much of the previous theories of magic passed on from classical antiquity in the writings of the Hermetic corpus and Neoplatonic thought. He wrote at a time when alchemists were beginning extensive studies with metals, and he sought to propagate a theory metallic magic to supplement or supplant the older magic which concentrated on empirical herbal lore and angelic or spiritual manifestations. In addition to his own work on the newly discovered property of magnetism, he served as an influence for Franz Anton Mesmer’s (1734–1815) dissertation for the doctor of medicine degree. Mesmer’s theory of animal magnetism served as the initial basis of the psychological technique now known as hypnosis.