Alchemy

   Science (or pseudoscience) that studied the transformation of physical substances from one nature to another and attempted to discover, regularize, and apply the relationships and procedures discovered through observation and experimentation to perform useful works, not only the transmutation of base metals into gold but also the production of chemical medicines. In a general way, it was a precursor of modern chemistry, and until at least the 18th century the distinction between genuine chemical reactions and alchemical transmutations was vague.

   Alchemy was known in ancient times, often linked with jewellers and metallurgists; it passed from the ancients to medieval Arabic natural philosophers and from them, along with other Arabic science, to Christian scholars. Its theoretical foundation was belief in a hierarchical organization of the universe, a theory that seemed to support the idea that the material nature of one substance could be transformed into a different substance through some sort of manipulation. The whole field was given credibility by the vaguely Platonic idea that the entire universe, inorganic as well as organic, is alive.

   Sometimes alchemists sought to apply spiritual forces (angelic or demonic) to facilitate their work, and in that case they were practicing something very close to witchcraft. Alchemists observed astrological signs and sought to carry out their work when the influences of the stars would favor their goal. The desire for gold and other precious substances (such as gemstones) explains why individuals, even rulers, sometimes granted subsidies to alchemists who promised to increase their wealth.

   Although making gold from base metals was the most common goal of alchemists, others sought to produce the "philosopher's stone," which supposedly had the power to heal disease, to prolong life, and to "perfect" metals. Similar medical and material advantage was believed to result from operations that produced the "quintessence" or fifth element. This fifth element was thought to possess great powers, including the power to cure disease and prolong life. Almost always, chemical learning was occult—that is, kept secret— and the alchemist normally claimed to have secret information that would ensure the success of his experiments even though others had failed. A particularly influential practitioner of alchemy was the unconventional physician Paracelsus.