Science » Lives of Scientists

The best books on Isaac Newton

recommended by William Newman

Interview by Benedict King

John Maynard Keynes famously cast Isaac Newton not as the first scientist of the age of reason, but the last of the magicians. How should we interpret the million words he wrote, in secret, on alchemy? What should we make of Newton's heretical religious views? William Newman talks us through the best books for a better understanding of the complex man who was one of the greatest physicists of all time.

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William Newman

William Newman is Distinguished Professor and Ruth N. Halls Professor in History and Philosophy of Science and Medicine at Indiana University, Bloomington.

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Before we talk about the books, it might be helpful if you could briefly put Isaac Newton into the context of the Scientific Revolution of the 17th century.  What was Newton’s contribution?

Isaac Newton co-discovered calculus with Gottfried Wilhelm Leibniz. He was the first person to truly quantify the universal law of gravity. He also was the first person to figure out that white light is actually an unaltered mixture of spectral colours. These were all radically new discoveries that completely transformed science.

Beyond that, he instituted the kind of style of doing science that amounted to looking for non-causal explanations, where you simply mathematize the relationships among natural phenomena without speculating about ultimate causes. The classic example is gravitational attraction; Newton resisted others’ attempts to get him to explain the cause of gravity. To him, it was enough to provide the mathematical explanation of it.

The first of the books about Isaac Newton you’ve chosen is a biography, Never at Rest by Richard Westfall. Is this the biography of Newton to read?

It’s a magisterial book. It’s the only treatment of Newton that really tries to give a detailed study of the totality of his science alongside his religion and his work on alchemy, which covered more than 30 years. It is a magnificent product. It’s somewhat dated now, because it appeared in 1980 and Newton scholarship has recently experienced a remarkable change. Some of the other books that I recommended represent attempts to come to terms with sections of Newton’s work in a deeper way than Westfall was able to do in 1980.

Part of the reason for that is because we now have digital sites like the Newton Project in the UK, which has been editing Newton’s theological and religious writings—his prophetic writings more generally—and then the Chymistry of Isaac Newton site that I am the general editor of at Indiana University, that’s been editing the alchemical papers, Newton’s work on chemistry. Westfall didn’t have access to all of that in 1980. So there’s a lot of material that Westfall wasn’t able to take account of, yet all the same, his work is a magnificent synthesis.

You mentioned Newton’s alchemical papers. His work on alchemy is your area of expertise and the subject of your latest book: Newton the Alchemist. Can his alchemical work be seen as foundational for modern science or was it a dead end?

There is currently a widespread ‘master narrative’ of Newton’s alchemy, though one with which I disagree. The major scholars of the subject at that time, especially Westfall, argued that the impact of alchemy on Newton’s more mainstream science lay in his emphasis on invisible forces that could act over a considerable space, such as gravitational attraction. The reason why a lodestone attracted iron at a distance was because of a hidden sympathy between the two, like the occult sympathies governing magical phenomena. Couldn’t this sort of explanation have stimulated Newton to think of gravity in terms of an immaterial attraction? And wasn’t alchemy based on the idea that some materials react with others because of a similar principle of affinity? Thus the idea that Newton’s involvement with alchemy was part of a quest to understand gravitational attraction was born. Contemporary sources ranging from popular outlets such as Wikipedia to serious scholarly monographs echo this theme.

In reality, however, there is little to no evidence to support the view that alchemy led to Newton’s belief in action at a distance. Instead, Newton’s alchemical research had a serious impact on his optics, as I explain in Newton the Alchemist, and it also contributed to his work on the short-range forces operating in chemical reactions, which the eighteenth century called ‘elective affinity.’ Newton came to be seen as the patron saint of elective affinity, thanks to a section of his famous 1717 Opticks that dealt with the theme of chemical attraction.

The next book is A Portrait of Isaac Newton by Frank Manuel, which is also a biography. It starts with his childhood in Lincolnshire and has chapters on his time at Cambridge and then in public life in London. What does it add to the story that Westfall doesn’t?

Manuel’s book was published in 1968, so it’s considerably earlier than Westfall’s. Manuel was a brilliant historian and perhaps an even more brilliant writer. I personally think that, of all the books written on Newton, his is stylistically the most engaging. It’s just a terrific read.

The book attempts to provide a kind of Freudian psychoanalytic study of Newton’s character. He tries to explain Newton’s psychology in terms of his childhood lack of a father. One thing that’s interesting about Manuel—and for that matter Westfall and almost everybody else who has come later—is that all these folks were influenced to some degree, perhaps without even realizing it, by John Maynard Keynes.

There was a famous Sotheby’s auction of Newton manuscripts by his heirs in 1936 and Keynes managed to acquire about half of them. Most of them he subsequently gave to King’s College Cambridge, where they remain, but he wrote an extraordinary article called “Newton the Man” which was published posthumously in 1947. In it, he argues famously that Newton was not the first scientist of the age of reason, but rather the last of the magicians. He tries to debunk the 18th-century view of Newton as a supreme rationalist and even possibly a deist. [Deists, in the 18th century, were people who believed in a supreme benevolent being who had set the universe in motion, but rejected the notion of an interventionist Christian God]

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One of the things that Keynes says in that essay is that Newton was “profoundly neurotic.” He portrays him as a solitary eccentric who was locked up in his study for 25 years or so in Cambridge, producing tremendously brilliant works and doing his alchemy in total isolation. That was Keynes’ view of Newton’s personality and character, and it was picked up by Manuel and dressed up in psychoanalytic clothing. It was subsequently adopted by Westfall as well and some other scholars, I would argue. So it’s impossible to discuss people like Manuel and Westfall without understanding the influence of Keynes. I didn’t put the Keynes piece on the list, but perhaps I should have done. It’s only eight or nine pages long and you can find it easily online.

This focus on Newton’s non-scientific side leads us neatly to the next of the books you’ve selected, Newton and the Origins of Civilization by Buchwald and Feingold. This is the latest word on Newton’s biblical-chronological studies.

Jed Buchwald and Mordechai Feingold point out that in the 17th century there was a widespread view among alchemists that the totality of ancient mythology was just encoded alchemy. There are many examples one could give, but I’ll stick with one that comes up in Newton’s “Index Chemicus”, a very long concordance of the alchemical writings that he read. He talks about Osiris, the Egyptian god, as being a sort of salt. He’s relying there on a 17th-century alchemist named Michael Maier, who interpreted Egyptian mythology as encoded alchemy. Maier argued that these stories about the Egyptian gods and goddesses and so forth were actually recipes that were dressed up as though the Egyptians were talking about actual divinities. That was the view of Maier and Newton interprets Maier in his own work on alchemy.

But in other writings on chronology Newton interprets Osiris literally as a god, though in a certain, restricted sense. Newton in his chronological writings worked with Euhemerus’s interpretation of mythology, in which the gods and goddesses of the ancients were originally human beings who were then treated as heroes and catasterised, so to speak, into the heavens as divinities. In other words, his chronological theory based on Egyptian mythology runs directly at odds with the alchemical theory of ancient mythology that he’s taking from Michael Maier. These are very distinct ways of looking at mythology. They are in fact contradictory and mutually exclusive.

I would argue that Newton did not himself believe that the ancients were encoding alchemy in their mythology. Instead, I suspect he thought people like Michael Maier were using mythology as a way of writing alchemical riddles that then had to be decoded if one was going to carry their alchemy into practice.

Part of the book is about the attacks on Newton in England and France and the demise of the science of chronology. Could you tell us a bit about that?

Newton was trying to build his chronology of the ancient world through studying the Bible and using what he knew about mythology. He really thought that you could extract actual dates out of biblical and mythological literature, with the help of astronomy and other scientific tools that he had at his disposal. For example, he tries to date Jason and the Argonauts’ adventures according to what he knew about the precession of the equinoxes. There’s a precession of one degree every 72 years, so he was able to work backwards from what he knew about the position of the equinoctial colures in the 1680s and 1690s and later.

So he’s incorporating astronomical material as a way of pinpointing the dates that he gets from ancient literature. That fell out of style after Newton’s death and by the 19th century it was considered rather ridiculous.

Another key feature of the book is the fact that Feingold and Buchwald have a very different view of Newton’s anti-trinitarianism than the one you get in other writers like Westfall.

So Newton didn’t believe in the Trinity, which was a highly controversial and dangerous position at at that time. In what way do Feingold and Buchwald offer a different view?

Again we need to go back to Keynes. Keynes thought that Newton was a heretic, that he is an anti-trinitarian from the early 1670s, if not earlier. That position has been picked up by other people, for example Westfall. The evidence for it is primarily the fact that Newton refused to take holy orders in 1675. Entering holy orders was a condition of his fellowship at Trinity College. He managed to get a special dispensation and, according to Westfall, Keynes, and various others, the reason why he refused to take holy orders was because he was effectively a crypto-heretic and would not agree to swear that the Trinity—in which the Father, Son, and Holy Spirit are of the same ‘substance’—was a legitimate way of interpreting Christianity.

Buchwald and Feingold argue otherwise. They suggest that Newton did not become an anti-trinitarian until at the very earliest 1679 and possibly later, and that his reason for rejecting holy orders was simply because he wanted to do scientific research unencumbered by religious duties. So it’s a radically different interpretation.

How does that fit with the next book, Rob Iliffe’s Priest of Nature, because he talks at some length about Newton’s heterodox anti-trinitarianism?

Iliffe takes a noncommittal position in Priest of Nature. There’s no question, of course, that Newton was a heretic. The problem is when did he commit to that idea? Most of his papers on his theological views date from, at the earliest, the 1680s. So there really isn’t much evidence from the 1670s. Iliffe spends a lot of time in his book arguing that Newton came out of a Puritan background and that he was intensely religious from day one. He argues that Newton was heavily influenced by an apothecary named Clark with whom he lived in Grantham when he was a student there at the King’s School, and that the origins of his later heretical views are an outgrowth of this early and intense religiosity.

Newton then entered Trinity College, Cambridge in 1661. Among his papers is a list of his sins that he wrote out in 1662, some of which seem quite trivial, like stealing cherry cobs from a friend in Grantham. He also repents of having wanted to burn down the house of his mother and his stepfather, a guy named Barnabas Smith. To Iliffe these admissions provide evidence of a highly Puritanical young Newton, whereas Feingold and Buchwald regard them as aberrations and point to the relative absence of religious themes in Newton’s surviving student notebooks.

In terms of sins, threatening to burn down his stepfather’s house sounds like quite a serious one.

What happened was that Newton’s father died directly before  he was born in 1642. His mother remarried the rector of a nearby town named Barnabas Smith, but Barnabas Smith was not interested in having the infant Newton in his house. So, although the house was only a couple of miles away, Newton was raised by his grandmother rather than his mother. She lived with Barnabas Smith for seven years and then he died too. Newton was eleven when Barnabas Smith died and his mother came back to live with him.

This is the basis for Manuel’s psychoanalysis. He claims that Newton was essentially angry throughout his entire life because his mother had been snatched away from him by Barnabas Smith.

Can you tell us about his broader heresy: he wasn’t just anti-trinitarian, was he? He thought the church fathers were fraudulent as well. And he was a strong believer that religious pluralism was a good thing. Is that a fair characterization?

Yes, but it’s more complicated. On the one hand, Newton wanted to claim that in order to be a good Christian all you had to do was profess that Jesus was the Son of God, the Father, and that love was the guiding principle, so basic tenets of Christianity. On the other hand, he was vehemently anti-Catholic and this comes out very clearly in his manuscripts. He claims the Nicene Creed, where the Trinity becomes an official part of Christianity, was a “great Apostasy,” and that behind it was a diabolical influence that converted Christianity essentially into a kind of paganism.

So he was vehemently opposed to the Trinity and to the early upholders of the Trinity like the Church father, Athanasius. And he writes that monks are perverts and goes on like this time and time again throughout his manuscripts. So on the one hand he’s very open to a simple view of Christianity, on the other he thinks Catholicism is evil.

And is his objection to the Trinity that it has no biblical warrant?


The final book you’ve chosen is by Niccolo Guicciardini and it’s called Isaac Newton and Natural Philosophy. It’s a much more recent publication. What does this book add to the picture?

Guicciardini’s is the first synthetic book that really tries to incorporate what you could call the new Newton scholarship. He has read and analysed Newton and the Origin of Civilization, Buchwald and  Feingold’s work. He’s also quite familiar with Iliffe’s work. He knows some of my work on Newton’s alchemy and he really does try to come to a new synthesis. You get a picture of Newton not so much as a kind of psychopath—that you get in Manuel and to some degree Westfall—but rather Newton as a kind of ‘Caltech geek,’ as Mordechai Feingold has put it. He is somebody who’s on the spectrum, but is not outright crazy.

To what extent did Newton’s achievements in natural philosophy lead him or others to dismiss the views he held on biblical literalism and chronology?

I would say that Newton’s influence in natural philosophy ultimately led away from the very things that he was trying to push not just in chronology, but also in religion more generally. For example, the second edition of the Principia, his major work on gravitation and so forth, includes something called the “General Scholium”, which is an attempt to argue for the necessity of God as the being that orders the universe. That’s absent from the first edition of the Principia. Newton was clearly worried that his natural philosophical work was going to lead, if not directly to atheism, then to a kind of disregard for religion. So you see him inserting these attempts to link his natural philosophical ideas to the necessity of religion in various different works of his.

Another example would be in the 1717 edition of the Optics. The Optics contains so-called “queries” that are hypothetical and Newton frames them in the form of questions. The last query makes a strong argument against Descartes’s idea that there is a fixed amount of motion in the universe, that motion is just getting transferred from one microscopic corpuscle to another, and so that motion could go on forever. Newton argues directly against that and for the necessity of what he calls “active principles”, which ultimately clearly go back to God. He thinks there’s an active principle behind gravity, that there’s an active principle behind magnetism and that there’s an active principle behind electricity. Clearly he’s trying to link these natural phenomena back to the necessity for the existence of a divinity.

So he was very worried about this and he was right to be so. Ultimately the Newtonian world picture did make it unnecessary to invoke direct divine causation. This is one of the reasons why Newton doesn’t like Descartes, because he felt that Cartesianism would lead to atheism. But ultimately the same thing could be said of his own natural philosophy.

Did he address that directly?

In the “General Scholium” he argues very clearly not only that there is a God, but that God is the Lord, the ruler of all. He has a very Old Testament view of God, which is obviously related to his unitarianism. He thinks that Jesus was the son of God, but Jesus nonetheless is not part of God in the way that the trinitarians believe.

There’s another issue that is worth mentioning and that is the issue of compartmentalization of Newton’s thought, a topic that Iliffe discusses. Newton was essentially brilliant at everything that he undertook seriously. Obviously, he was particularly successful in the realm of natural philosophy, what we would call physics, but the same can be said of his religious writings. They really are highly original and extremely ingenious, even if you don’t believe them. The same can be said of his alchemical writing. He was making compounds that people may or may not have discovered even today.

This leads to a different question, which is, how did all of these different pursuits integrate or did they? I hinted at this earlier with the issue of chronology and alchemy and the interpretation of mythology, and how it seems that Isaac Newton was keeping the alchemical and the historical interpretations of mythology quite distinct.

The issue of compartmentalization has really come to the fore as a result of more and more rigorous scholarship on these different aspects of Newton’s thought. These works that I’ve recommended to you, in particular Buchwald and Feingold and Iliffe, are carrying out research on particular aspects of Isaac Newton’s thought in more and more detail. And so the question of how to deal with all of these different sides of Newton has become really very problematic. Guicciardini deals with this I think rather successfully, but nonetheless questions remain as to how you approach this extreme compartmentalization. Is there a relationship between Newton’s ideas on physics and his ideas on alchemy, for example, and if so, what is its precise character?

Even if Newton hadn’t found the unifying factor amongst all these things, Newton must have thought there must be some coherence between them.

I’m not sure that’s right. I don’t know. The problem is you have this guy who is clearly an out-of-control genius. Isaac Newton gets interested in something and he pursues it to the nth degree. He almost can’t control himself. It’s like he can’t turn his brain off. So he just happens to be incredibly good at almost anything he does. Let me give you a parallel example from personal experience. I had a colleague years ago, at Indiana University, who was a brilliant philosopher of science. He was also an Epicurean cook and he also was so good at playing the French horn that he was able to play it in an orchestra in a major city. Did he think all those things were connected? I’m not so sure.

If someone believes in a God who’s the author of the universe, then it implies there must be a coherence between all areas of knowledge. I suppose that’s why I thought he must he must have felt there was some sort of coherence between all these things—some underlying laws.

I think that’s true, but at such an abstract and general level that it might not even touch Isaac Newton’s actual work. For instance, Newton’s view of Christianity ultimately boiled down to very general precepts such as ‘Love thy neighbour,’ ‘Profess the reality of Jesus Christ as the Son of the Father,’ and that kind of thing. So all of the incredibly detailed work that he did in interpreting prophecy, for example, or in writing against the Trinity, may not really have interacted with those very general precepts in any significant way. Isaac Newton was a virtuoso at practically everything he undertook, and virtuosity in multiple areas of endeavour need not imply their interconnectedness.

The problem of assuming an underlying unity to Isaac Newton’s thought also emerges from an examination of his alchemy. The issue with alchemy is problematic because alchemical writings are often filled with references to God. And the reason for that I think is because alchemists themselves were constantly under threat of being accused of counterfeiting and so forth. So they tried to build up the picture of themselves as extremely religious people. I really think that’s the case. When [the Newton historian] Betty Jo Dobbs interpreted that material in his manuscripts she came to the conclusion that, ‘Yes, of course, this is really all about Isaac Newton’s religion.’ Yet there’s actually very little evidence to support Dobbs’s view, because if you look at the work Isaac Newton wrote on theology, there are practically no references to alchemy. In reality it appears that he kept these topics in fairly watertight compartments. So as historians we have to be very, very careful not to make assumptions. Typically we want to say all of these things are related, but maybe not. They may simply reflect virtuoso performances in a variety of unrelated or only loosely related areas rather than manifestations of a single underlying quest for unity.

Interview by Benedict King

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William Newman

William Newman is Distinguished Professor and Ruth N. Halls Professor in History and Philosophy of Science and Medicine at Indiana University, Bloomington.