John Dee owned the largest private library in Elizabethan England, advised the queen on matters from the calendar to the colonies, and wrote the preface that introduced English readers to Euclid. He is remembered mostly for the years he spent taking dictation from angels.

Both halves belong to the same man, and for Dee they were one project.

Dee was born in London on July 13, 1527. He took his degrees at St John's College, Cambridge, became a fellow of Trinity College in 1546, and then went abroad to study at Louvain with the mathematician Gemma Frisius and the mapmaker Gerardus Mercator. In Paris he lectured on Euclid and turned down a permanent post.

Back in England he made himself useful. He chose the day for Elizabeth I's coronation, which at the time was a technical service rather than an eccentric one. He advised the Muscovy Company's navigators, argued for calendar reform and English expansion overseas, and in 1570 wrote the preface to the first English translation of Euclid. His Monas Hieroglyphica of 1564, a dense treatise built around a single symbol, blended alchemy with Kabbalah and baffled readers then as now.

His house at Mortlake, near London, held the collection that made his reputation. Dee claimed more than 3,000 printed books and 1,000 manuscripts. A surviving catalog lists 2,292 printed items and 199 manuscripts. Either way, it was the largest private collection in England.

The scryer

For all that learning, Dee concluded that books would not give him what he wanted. If human scholarship fell short, he would ask higher authorities. He began experiments in crystal-gazing in 1581.

Dee needed a scryer, a medium to look into the stone and report what appeared. In 1582 he found one in Edward Kelley.

The method never changed. Kelley gazed and spoke. Dee sat beside him and wrote everything down, session after session. Dee later said that holy angels had been instructing him for years. What can be said with confidence is narrower: Kelley described visions, and Dee believed him. Every word of the angelic conversations came through Kelley's mouth.

A language from Eden

The most durable product of those sessions was a language. Through Kelley, the angels were said to dictate an alphabet, a vocabulary and a series of invocations in what Dee understood to be the tongue spoken before the fall of mankind. It is now known as Enochian.

Whether Kelley invented it, improvised it in a state of sincere conviction, or something in between is not recoverable from the evidence. Nothing in the record requires a supernatural explanation, and nothing in the record shows Dee suspecting a fraud.

In 1583 the two men and their families left England for the Continent, spending six years abroad, much of the time in Bohemia. The partnership ended in strange circumstances. Kelley reported an angelic command that the two men should hold their wives in common. Dee was appalled, recorded his distress, and complied. Dee returned to England in 1589.

The lost library

He came home to a wreck. Before leaving, Dee had put the library in the care of his brother-in-law, Nicholas Fromond, who, Dee complained, sold it off or let it be carried away almost as soon as he was gone. Hundreds of volumes ended up with a man named Nicholas Saunder, who appears to have tried to scrub out Dee's signature and write his own over it.

That clumsy cover-up is why the trail can still be followed. More than 100 of Dee's books, the largest surviving group in one place, are now in the library of the Royal College of Physicians in London, where they arrived in the 1680s with the collection of the Marquis of Dorchester. In 2016 the college put them on public display for the first time.

Dee's last years were thin. He held a modest post as a warden in Manchester and died at Mortlake in poverty. Sources give his death as December 1608 or March 1609. His reputation was fixed half a century later, in 1659, when Meric Casaubon published the spirit diaries as a warning against delusion.

The black mirror

The most famous object linked to Dee sits in the British Museum's Enlightenment Gallery: a disc of polished black obsidian, 18.4 centimeters across, kept in a tooled leather case. A label on the case, in the handwriting of the 18th-century collector Horace Walpole, identifies it as "The Black Stone into which Dr Dee used to call his Spirits."

It had long been assumed to be Mexican. In 2021 a team led by Stuart Campbell of the University of Manchester confirmed it. Writing in the journal Antiquity, the researchers reported that portable X-ray fluorescence, which reads the chemical fingerprint of volcanic glass without damaging it, matched the mirror to obsidian from Pachuca, a source heavily worked under the Aztec empire. Aztec craftsmen made such mirrors for divination, and they were associated with the god Tezcatlipoca, whose name means Smoking Mirror. Many were shipped to Europe after the Spanish conquest of 1521.

Two cautions belong beside the headline. The study established where the stone came from, not who owned it. There is no record of how or when Dee acquired the mirror, and its link to him rests on Walpole, who received it as a gift in 1770, more than a century and a half after Dee died. The attribution is plausible and widely accepted. It is not proven.

What Dee was after

It is tempting to split Dee in two and keep the half that suits: the navigator's mathematician or the necromancer. His own age did not draw the line there. Astrology was applied astronomy, alchemy was chemistry with ambitions, and a universe written in number might reasonably be read by anyone, human or otherwise, who knew the script.

Dee's error was not that he abandoned reason for superstition. It was that he took one unverifiable witness at his word for years. The mirror, if it was his, makes the point neatly: an instrument of Aztec divination, carried across an ocean by conquest, repurposed by an English scholar to ask heaven for the answers his three thousand books had not given him.