Paracelsus pseudonym of Theophrastus Bombastus von Hohenheim (1493–1541), Swiss chemist, physician, and natural philosopher. He pursued medical studies at various German and Austrian universities, probably completing them at Ferrara (1513–16). Thereafter he had little to do with the academic world, apart from a brief and stormy period as professor of medicine at Basle (1527–28). Instead, he worked first as a military surgeon and later as an itinerant physician in Germany, Austria, and Switzerland. His works were mainly in German rather than Latin, and only a few were published during his lifetime.
His importance for medical practice lay in his insistence on observation and experiment, and his use of chemical methods for preparing drugs. The success of Paracelsian medicine and chemistry in the later sixteenth and seventeenth centuries was, however, largely due to the theoretical background he provided. He firmly rejected the classical medical inheritance, particularly Galen’s explanation of disease as an imbalance of humors; he drew on a combination of biblical sources, German mysticism, alchemy, and Neoplatonic magic as found in Ficino to present a unified view of humankind and the universe. He saw man as a microcosm, reflecting the nature of the divine world through his immortal soul, the sidereal world through his astral body or vital principle, and the terrestrial world through his visible body. Knowledge requires union with the object, but because elements of all the worlds are found in man, he can acquire knowledge of the universe and of God, as partially revealed in nature. The physician needs knowledge of vital principles (called astra) in order to heal. Disease is caused by external agents that can affect the human vital principle as well as the visible body. Chemical methods are employed to isolate the appropriate vital principles in minerals and herbs, and these are used as antidotes. Paracelsus further held that matter contains three principles, sulfur, mercury, and salt. As a result, he thought it was possible to transform one metal into another by varying the proportions of the fundamental principles; and that such transformations could also be used in the production of drugs. See also ALCHEMY, MYSTICISM. E.J.A.