Alchemy gets a bad press. It has done for centuries. Changing base metal into gold is, at best, a delusional dream and at worst a con-trick, a shyster’s brag. In Ben Jonson’s play The Alchemist, Subtle is an unashamed charlatan who promises his clients limitless wealth through access to the Philosopher’s Stone. One of The Canterbury Tales – The Canon’s Yeoman’s Tale – revolves around the story of a canon selling a pot capable of producing silver at will. Recent scholarship has suggested that Chaucer was familiar with a real case where a chaplain claimed, through alchemical practice, to be able to conjure coins of silver and gold which he then sold to the Mint for a tidy profit.

Isaac Newton’s interest in alchemy is well-known. His work on physics was dwarfed by the vast corpus of unpublishable material on alchemy and the occult. In 1936, John Maynard Keynes bought a sheaf of his manuscripts and spent years trying to unravel their arcane weavings. His conclusion challenged Newton’s pre-eminent position in the scientific pantheon: ‘Newton was not the first of the age of reason. He was the last of the magicians, the last of the Babylonians and Sumerians, the last great mind which looked out on the visible and intellectual world with the same eyes as those who began to build our intellectual inheritance rather less than 10,000 years ago.’ Newton’s early biographers suppressed this less empirical side of his work, lest it undermine his authority. Newton himself kept it quiet – as well he might. Many alchemical practices were banned at the time and punishment for conviction reputedly included hanging from a gallows wrapped with silvery tinsel.

In Russia, Peter the Great’s favourite scientist was Count Iakov Brius – son of a Scottish immigrant. They travelled together to London on Peter’s notorious Grand Embassy, and Brius stayed on for six months to study science and collect scientific instruments. Back in Moscow, he set up an observatory in the Sukharev Tower, ran a School of Navigation, built Russia’s first Newtonian telescope, promoted Copernican astronomy, and commissioned and wrote a good deal of science and mathematics. Yet he is remembered in Russia as Koldun na Sukharevoi bashne ‘the wizard in the Sukharev Tower’ (the title of a nineteenth-century novel about him by Ivan Lazhechnikov) – the man who turned silver into gold and owned a book written by the devil himself. In 1934, Stalin demanded the tower be destroyed, and everything in it brought to him. As the demolition took place, so the story goes, a tall man in a powdered wig was spotted in the crowd, jabbing an accusing finger at the work.

The popular image of alchemy, of the transmutation of metals, is a misunderstanding, a corrupt simplification. Alchemy embraces a hugely sophisticated set of beliefs and practices, and a high-minded cosmology. The universe is not static but a dynamic system on a very slow trajectory towards ultimate perfection. At the heart of all matter lies the prima materia.  The natural world is struggling to restore it, to shake off all the impurities and return Creation to its harmonious state. What alchemy offers is a participation in this process, an acceleration of it, requiring only the discovery of lapis philosophorum as agent to convert substances into the prima materia. The quest for the Philosopher’s Stone was not so different from the cathartic promises of most religions – but rather than temple and priest, it involved furnaces and alembics and distillation vessels, all the paraphernalia of a laboratory.

In recent years, the study of alchemy has enjoyed something of a revival. Its importance in the history of science is becoming much more widely understood. Serious scholarship and international symposia are conducted in its name. Newton’s esoterica are now on-line, through the Cambridge Digital Library. Yet overturning centuries of prejudice does not come easily. One of the principal revisionists, Lawrence Principe of John Hopkins University, was recently ‘yelled at’ in a conference for discussing alchemy and accused of taking ‘hallucinatory drugs’.

Alchemy has its origins in the great ferment of Alexandria in the early Christian centuries. The ideas of Gnostics and Neoplatonists were combined with those of Babylon and ancient Egypt. One of the earliest texts, written by a pupil of Democritus, is the Physika kai Mystika – ‘Of Natural and Hidden Questions’. It is the adventure of hidden questions that really drove the alchemists, the Platonic idea that we live in a world that is only partially visible. To try and glean the veiled elements of our world was the Opus Magnum of alchemy.

The great fifteenth-century alchemist, Sir George Ripley, was not alone in recognizing the mysterious nature of his enthusiasm. The Philosopher’s Stone would enable the ultimate reduction of matter. It was substance, but spirit too. It was elusive, but ubiquitous: ‘The philosophers say that the birds and fishes bring the Stone to us, each man possesses it, it is everywhere, in you, in me, in all things’. Reach the heart of things and you find enigma, paradox, ambiguity. That is the legacy of the alchemists. It is also what Einstein discovered, and what the pioneers of particle physics and mathematics are discovering too. The zealots of the Enlightenment did their best to purge it from the new scientific tradition; now that tradition has matured, the role of alchemy can be properly examined.