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The modern world as we know it simply would not exist if not for the mind of Sir Isaac Newton. His synthesis of differential calculus and pioneering research on the nature of gravity and light are bedrocks of the scientific method. However in his later years, Newton’s interests were admittedly drawn towards a decidedly non-scientific subject, alchemy. Does that investigation invalidate Newton’s earlier achievement, asks theoretical physicist and philosopher, Carlo Rovelli in the excerpt below. His new book of correspondence and musings, There Are Places in the World Where Rules Are Less Important than Kindness: And Other Thoughts on Physics, Philosophy and the World, Rovelli explores themes spanning from science to history to politics and philosophy.  

Riverhead Books

From THERE ARE PLACES IN THE WORLD WHERE RULES ARE LESS IMPORTANT THAN KINDNESS: And Other Thoughts on Physics, Philosophy and the World by Carlo Rovelli published on May 10, 2022 by Riverhead, an imprint of Penguin Publishing Group, a division of Penguin Random House LLC. Copyright © 2022 Carlo Rovelli.

In 1936 Sotheby’s puts up for auction a collection of unpublished writings by Sir Isaac Newton. The price is low, £9,000; not much when compared to the £140,000 raised that season from the sale of a Rubens and a Rembrandt. Among the buyers is John Maynard Keynes, the famous economist, who was a great admirer of Newton. Keynes soon realizes that a substantial part of the manuscript writings deal with a subject that few would have expected Newton to be interested in. Namely: alchemy. Keynes sets out to acquire all of Newton’s unpublished writings on the subject, and soon realizes further that alchemy was not something that the great scientist was marginally or briefly curious about: his interest in it lasted throughout his life. “Newton was not the first of the Age of Reason,” Keynes concludes, “he was the last of the magicians.” 

In 1946 Keynes donated his unpublished Newtoniana to the University of Cambridge. The strangeness of Newton in alchemical guise, seemingly so at odds with the traditional image of him as the father of science, has caused the majority of historians to give the subject a wide berth. Only recently has interest in his passion for alchemy grown. Today a substantial amount of Newton’s alchemical texts have been put online by researchers at Indiana University and are now accessible to everyone. Their existence still has the capacity to provoke discussion, and to cast a confusing light over his legacy. 

Newton is central to modern science. He occupies this preeminent place because of his exceptional scientific results: mechanics, the theory of universal gravity, optics, the discovery that white light is a mixture of colors, differential calculus. Even today, engineers, physicists, astronomers and chemists work with equations written by him, and use concepts that he first introduced. But even more important than all this, Newton was the founder of the very method of seeking knowledge that today we call modern science. He built upon the work and ideas of others — Descartes, Galileo, Kepler, etc — extending a tradition that goes back to antiquity; but it is in his books that what we now call the scientific method found its modern form, immediately producing a mass of exceptional results. It is no exaggeration to think of Newton as the father of modern science. So, what on earth does alchemy have to do with any of this? 

There are those who have seen in these anomalous alchemical activities evidence of mental infirmity brought on by premature aging. There are others who have served their own ends by attempting to enlist the great Englishman among critics of the limitations of scientific rationality. 

I think things are much simpler than this. 

The key lies in the fact that Newton never published anything on alchemy. The papers that show his interest in the subject are extensive, but they are all unpublished. This lack of publication has been interpreted as a consequence of the fact that alchemy had been illegal in England since as early as the fourteenth century. But the law prohibiting alchemy was lifted in 1689. And besides, if Newton had been so worried about going against laws and conventions, he would not have been Newton. There are those who have portrayed him as some kind of demonic figure attempting to glean extraordinary and ultimate knowledge that he wanted to keep exclusively for himself, to enhance his own power. But Newton really had made extraordinary discoveries, and had not sought to keep those to himself: he published them in his great books, including the Principia, with the equations of mechanics still used today by engineers to build airplanes and edifices. Newton was renowned and extremely well respected during his adult life; he was president of the Royal Society the world’s leading scientific body. The intellectual world was hungry for his results. Why did he not publish anything based on all those alchemical activities?

The answer is very simple, and I believe that it dispels the whole enigma: he never published anything because he never arrived at any results that he found convincing. Today it is easy to rely on the well-digested historical judgment that alchemy had theoretical and empirical foundations that were far too weak. It wasn’t quite so easy to reach this conclusion in the seventeenth century. Alchemy was widely practiced and studied by many, and Newton genuinely tried to understand whether it contained a valid form of knowledge. If he had found in alchemy something that could have withstood the method of rational and empirical investigation that he himself was promoting, there can be no doubt that Newton would have published his results. If he had succeeded in extracting from the disorganized morass of the alchemical world something that could have become science, then we would surely have inherited a book by Newton on the subject, just as we have books by him on optics, mechanics and universal gravity. He did not manage to do this, and so he published nothing.

Was it a vain hope in the first place? Was it a project that should have been discarded even before it began? On the contrary: many of the key problems posed by alchemy, and quite a few of the methods it developed, in particular with reference to the transformation of one chemical substance into another, are precisely the problems that would soon give rise to the new discipline of chemistry. Newton does not manage to take the critical step between alchemy and chemistry. That would be down to scientists of the next generation, such as Lavoisier, to achieve. 

The texts put online by Indiana University show this clearly. It is true that the language used is typically alchemical: metaphors and allusions, veiled phrases and strange symbols. But many of the procedures described are nothing more than simple chemical processes. For example, he describes the production of “oil of vitriol” (sulfuric acid), aqua fortis (nitric acid) and “spirit of salt” (hydrochloric acid). By following Newton’s instructions, it is possible to synthesize these substances. The very name that Newton used to refer to his attempts at doing so is a suggestive one: “chymistry.” Late, post-­Renaissance alchemy strongly insisted on the experimental verification of ideas. It was already beginning to face in the direction of modern chemistry. Newton understands that somewhere within the confused miasma of alchemical recipes there is a modern science (in the “Newtonian” sense) hidden, and he tries to encourage its emergence. He spends a great deal of time immersed in it, but he doesn’t succeed in finding the thread that will untie the bundle, and so publishes nothing.

Alchemy was not Newton’s only strange pursuit and passion. There is another one that emerges from his papers that is perhaps even more intriguing: Newton put enormous effort into reconstructing biblical chronology, attempting to assign precise dates to events written about in the holy book. Once again, from the evidence of his papers, the results were not great: the father of science estimates that the beginning of the world happened just a few thousand years ago. Why did Newton lose himself in this pursuit?

History is an ancient subject. Born in Miletus with Hecataeus, it is already fully grown with Herodotus and Thucydides. There is a continuity between the work of historians of today and those of antiquity: principally in that critical spirit that is necessary when gathering and evaluating the traces of the past. (The book of Hecataeus begins thus: “I write things that seem to me to be true. For the tales of the Greeks are many and laugh‑ able as they seem to me.”) But contemporary historiography has a quantitative aspect linked to the crucial effort to establish the precise dates of past events. Furthermore, the critical work of a modern historian must take into account all the sources, evaluating their reliability and weighing the relevance of information furnished. The most plausible reconstruction emerges from this practice of evaluation and of weighted integration of the sources. Well, this quantitative way of writing history begins with Newton’s work on biblical chronology. In this case too, Newton is on the track of something profoundly modern: to find a method for the rational reconstruction of the dating of ancient history based on the multiple, incomplete and variably reliable sources that we have at our disposal. Newton is the first to introduce concepts and methods that will later become important, but he did not arrive at results that were sufficiently satisfactory, and once again he publishes nothing on the subject. 

In both cases we are not dealing with something that should cause us to deviate from our traditional view of the rationalistic Newton. On the contrary, the great scientist is struggling with real scientific problems. There is no trace of a Newton who would confuse good science with magic, or with untested tradition or authority. The reverse is true; he is the prescient modern scientist who confronts new areas of scientific inquiry clear-sighted, publishing when he succeeds in arriving at clear and important results, and not publishing when he does not arrive at such results. He was brilliant, the most brilliant—but he also had his limits, like everyone else.

I think that the genius of Newton lay precisely in his being aware of these limits: the limits of what he did not know. And this is the basis of the science that he helped to give birth to.