How to understand Newton’s obsession with alchemy in his later years

　　The saying that “Newton was obsessed with alchemy in his later years” is a misunderstanding. Newton did collect a lot of information on alchemy, wrote many manuscripts related to alchemy, and did many experiments that alchemists had done, but what he was obsessed with was not the desire to turn stones into gold, nor the desire to live forever. Instead, he tried to find scientific evidence that matched his own scientific hypothesis in the cumbersome alchemy materials.
　　The relationship between Newton and alchemy was not known to the public during his lifetime. The reason is that the manuscripts related to alchemy left by him have not been made public for more than two hundred years.
　　In 1727, Newton died. His relatives collected all the papers and manuscripts in his house. In order to maintain Newton’s historical image, the manuscripts related to alchemy were classified as “unsuitable for publication” and dust-sealed.
　　In 1936, this batch of documents, including manuscripts related to alchemy, was taken to Sotheby’s auction house in the UK and divided into 322 public auctions, with a total auction price of about 10,000 pounds.
　　Later, these alchemy-related manuscripts (including many biographical materials of Newton) were gathered into his own hands by the British economist Keynes. According to these manuscripts, Keynes wrote the article “Newton and the Man”, saying that Newton “was not the first man in the age of reason, but the last magician”. This article was included in the “Newton 300th Anniversary Papers” published by the Royal Society in 1946. The relationship between Newton and alchemy thus forms an important topic in the history of science.
　　Based on the ancient theory that the world is made up of the four elements of earth, air, water, and fire, alchemists believed that if they found the right method, they could change one substance into another. This kind of effort mainly focuses on two directions: finding something that can transform base metals such as iron and lead into precious metals such as gold and silver; refining a substance that can make people immortal and youthful.
　　As early as the 1760s, Newton had read the writings of George Starkey, a famous alchemist in London at the time. Around 1670, he began to read a lot of alchemical materials, and compiled an index to group the terms and expressions collected from alchemical works-although almost all alchemists claimed to have mastered alchemy, they all had no knowledge of alchemy. The recipe is kept secret and the terminology used varies. Newton’s experimental research on alchemy continued until at least 1696 (and document research until his death)—the year he left Cambridge to take up the post of Superintendent of the Royal Mint.
　　Why was Newton interested in alchemy? For this question, the interpretation of “Cambridge History of Science” is as follows:
　　The most important alchemist in the 18th century was Newton. … Newton scoured the literature of alchemy throughout most of his career, amassed a vast collection of records, and transcribed the entire treatise himself. He immersed himself in an intense cycle of experiments and wrote extensive reports on his discoveries. He tried to find the alchemist’s evidence of the universal living soul, through which he believed that God was constantly influencing the world: for him, gravitation, alchemy, Art and God are closely linked. Newton’s pursuit of alchemy was not subordinate to his natural philosophy, but formed an essential part of his religious endeavors to study the activities of God in as many ways as possible.
　　This explanation unifies Newton’s efforts in natural science, alchemy, and theology into the general direction of “studying the activities of God”, which is evidenced by Newton’s own words. In 1675, Newton got a manuscript of alchemy from a friend. He wrote the following paragraph in the front of the manuscript:
　　Alchemy does not deal with metals as ignorant laymen think… On the contrary, it (alchemy Philosophy) is beneficial and enlightening, firstly to help you learn about God, and secondly to help you find the way to discover real medicine from creation. Praise God, teach people how to live well, and always help your neighbor and keep a good heart.
　　In Newton’s world view, “God” is an extremely important existence. The alchemical manuscripts left by Newton have a total of about 650,000 words, far exceeding the sum of his physics and mathematics research; his theological research manuscripts have a total of more than 1.3 million words. From this size comparison, it is not difficult to see that in his value system, “to praise God by understanding God’s wonderful deeds” is at the core. It is worth noting that Newton’s theological research and research were far from the mainstream theology at that time, and it could even be said that he was a criticism of the mainstream theology, which was a kind of “deviance”.
　　However, “Cambridge History of Science” said that Newton’s research on alchemy “does not belong to his natural philosophy”, this assertion is open to question.
　　First of all, the academic theory used by Newton to examine alchemy is no longer the “four elements theory” of traditional alchemists. He was influenced by the “particle philosophy” of Robert Boyle, a British chemist and physicist who was also his teacher and friend. This philosophy believes that what constitutes objects and even the world is the smallest particle in nature; this particle is created by God and endows them with movement and activity; particles can condense with each other to form first-level particles, and the first-level particles condense with each other Secondary particles can be formed… until all kinds of complex objects are formed. According to this hypothesis, as long as an agent can be found that can destroy stable particles and disintegrate them into the smallest particles, and then under the action of some active elements, these particles can recondense into a new object. Based on this new academic hypothesis, the pursuit of alchemy to transform base metals into precious metals naturally entered the vision of Boyle and Newton.
　　Secondly, apart from academic tools, the biggest difference between Newton and Boyle, the two “new alchemists” and traditional alchemists, is that their pursuits are opposite. Traditional alchemists pursued wealth and status, so they cared most about how to “turn stones into gold”, that is, transform gold; Newton and Boyle pursued the verification or falsification of scientific hypotheses, so they cared most about how to destroy gold. Disintegrate it into the smallest particles, that is, destroy the gold—gold is a very stable metal, if there is an agent that can destroy gold into the smallest particles, it is equivalent to the confirmation of the “microparticle philosophy” Take the first step. Based on this difference in pursuit, Boyle and Newton lacked favor for traditional alchemists.
　　In the middle and late stages of alchemy research, in order to explain some experimental phenomena, Newton introduced the concept of “particle force” into the “particle philosophy”. For example, he observed that nitric acid can dissolve silver but not gold, and aqua regia can dissolve gold but not silver (according to the explanation of modern chemistry, this observation is not complete), so he made a speculation: “Can it be said that the particles of nitric acid Fine enough to penetrate both silver and gold, but lacks the attraction to make it penetrate gold? And the particles of aqua regia are fine enough to penetrate gold and silver, But it lacks the attraction to make it drill into the silver?”
　　From today’s point of view, this speculation is obviously wrong. Everything that happens between nitric acid, aqua regia and gold and silver must be explained by chemical reactions between various elements. But this does not mean that Newton’s efforts are worthless, nor does it mean that Newton is not pursuing science, nor does it mean that Newton is following the old path of traditional alchemy. The tree of science is developed through countless times of “hypothesis-falsification/confirmation”. No scientist can guarantee that his hypothesis will always be on the right path, and Newton is no exception.
　　In short, in Newton, theology and science are self-consistent. The common saying in the Chinese intellectual circles that “Newton turned to theology in his later years and indulged in alchemy” is not true-the so-called turn does not exist, and the so-called obsession is just a misunderstanding.