His thought was colored by the fantastic philosophies of his time and he based his medical theories on the concept of human beings as microcosms of the universe. He was firmly opposed to the humoral theory of disease championed by Galen, and he advocated the use of specific remedies for specific diseases, introducing many chemicals (e.g., laudanum, mercury, sulfur, iron, and arsenic) into use as medicines. He also noted relationships such as the hereditary pattern in syphilis and the association of cretinism with endemic goiter and of paralysis with head injuries. Paracelsus wrote numerous medical and occult works containing a curious mixture of sound observation and mystical jargon. His work On Diseases of Miners was the first study devoted to an occupational disease.
See Four Treatises of Theophrastus von Hohenheim (ed. by H. E. Sigerist, 1941); biographies by W. Pagel (2d ed. 1982) and C. Webster (2008).