BOOKS ET AL. 21 DECEMBER 2012 VOL 338 SCIENCE www.sciencemag.org 1540 E arly in the 1940s, John Maynard Keynes composed an ambivalent trib- ute to Isaac Newton ( 1). Since the Enlightenment, Newton had been remem- bered “as the first and greatest of the mod- ern age of scientists, a rationalist, one who taught us to think on the lines of cold and untinctured reason.” But Newton’s long- suppressed manuscripts— many of which Keynes him- self bought at auction and presented to King’s College Cambridge—told a differ- ent story. The real Newton was an “unbridled addict” of alchemy. He had tried for decades to “read the riddle of tradition, to find meaning in cryptic verses, to imitate the alleged but largely imaginary experiments of the initiates of past centu- ries.” Keynes described the thousands of pages Newton had devoted to this pursuit as “wholly magical and wholly devoid of scien- tific value.” Over the past half-century, historians of alchemy—especially William Newman and Lawrence Principe—have taught us to see the papers that dismayed Keynes in a very different light. The alchemy Newton prac- ticed was a genuine scientific tradition, which took shape over centuries and involved both hands-on experimentation and sophisticated theories. In The Secrets of Alchemy , Principe has pulled together the threads of his research and that of many colleagues. This ele- gant, readable book, packed with information and reve- lation, covers the history of alchemy from its shadowy origins in Hellenistic Egypt to its scholarly recovery in the 20th century. Principe traces the contours of a mil- lennial tradition and shows exactly why Newton and many other brilliantly gifted scientists found so much promise in it. The story is not simple: nothing about alchemy is. Alchemists often presented their findings in a deliberately obscure way. They used pseudonyms, forged supposed ancient authorities, and identified vital ingredients with Decknamen (code names), often based on a metaphorical connection to the actual substances to be used. And they pursued many goals, small and large. The search to transmute base metal into gold was only one thread in an immense and var- ied tapestry. More important, alche- mists often disagreed about basic points: for example, whether substances produced by alchemy could ever match those produced by nature. Avicenna insisted that they could not; Roger Bacon argued, just as strongly, that they could. Medicine has served as both a model for alchemy, seen as therapy for metals, and an application for it, especially thanks to its vociferous Renaissance practi- tioner Paracelsus. Early alchemical texts are likely to baffle the modern reader who confronts them for the first time. Basic elements of the art—like the numerological systems used by early alche- mists to grade the transformative powers of particular substances—seem arbitrary, if one does not realize that many saw numbers and their ratios as keys to a deeper reality. Many alchemists explicitly stated that their discov- eries came not only from direct, dirty-handed manipulation of metals and acids but also from divine revelations, which they received, and reported, in the form of complex visions. For all the air of mystery, Principe shows, alchemy has always had a strong hands-on component. Alchemical practitioners inter- acted with makers of coins, miners, dyers, and others who knew materials and their powers directly. Even the most abstract or mythical- sounding texts are often enciphered recipes. Watching Principe decode a set of images and words and then carry out the manipula- tions they call for is as exciting as watching a skilled magician carry out his best tricks. Basil Valentine—the pseudonym for a group of Renaissance alchemical writers— instructs the reader: “the king’s crown should be pure gold, and a chaste bride should be married to him. Take the ravenous grey wolf … [that] by birth is a child of old Saturn…. Throw the king’s body before him.” It sounds (and the associated image looks) completely bizarre. To Principe, though, the “riddle is rel- atively easy.” He identifies the king as gold, the king of the metals. Saturn is lead, so his child should be something related to lead: antimony ore or stibnite. Suddenly it all makes sense. Throw a piece of impure gold into melted stib- nite, Principe explains, and it dissolves very rapidly, producing a brilliant white alloy. Again and again, Principe melds rich his- torical erudition with deft chemical manip- ulation. The results are always convincing and sometimes—as when one recipe yields a golden object in the form of a tree—breathtaking. And the upshot of it all is clear. Newton and his fellow afi- cionados, who included Boyle, Hooke, and Leib- niz, had every reason to believe that alchemy might yield profound knowledge about nature. They had not only read enticing texts and heard astonishing stories by the dozen but also wit- nessed dramatic demonstra- tions of what chymistry— Principe’s and Newman’s term for what they prac- ticed—could actually do. In the end—and here Principe’s historical work is at its most subtle and acute—the point is not sim- Of Chymists and Kings HISTORY OF SCIENCE Anthony Grafton The reviewer is at the Department of History, Princeton University, Prince- ton, NJ 08544–1017, USA. E-mail: grafton@princeton.edu The Secrets of Alchemy by Lawrence M. Principe University of Chicago Press, Chicago, 2013. 295 pp. $25, £16. ISBN 9780226682952. An Alchemist in His Workshop (David Teniers II, 17th century). Published by AAAS