Jean Taisner

Jean Taisner: The Thief Who Saved Two Books

In 1574 the Venetian mathematician Giovanni Battista Benedetti opened a book with an accusation. Someone, he wrote, "so completely took for himself our little work, that he altered nothing except the name of the author." The someone was Jean Taisnier, choirmaster to the Archbishop of Cologne, and Benedetti was right. What Benedetti could not have known is that the theft would carry his own ideas further than his original ever had — to Kepler, to the Collegio Romano, and into English.

The Merchant's Son from Ath

He was born in 1508 in Ath, in the County of Hainaut, then part of the Habsburg Netherlands — a Walloon, and he signed himself Hannonius to say so. His father Thomas Taisnière was a prosperous merchant, dead before 4 October 1522, leaving Jean with siblings named Françoise, Joachim and Pierchon. Jean was, more distantly, the great-uncle of the painter David Teniers the Elder.

He took his first schooling in Ath and then read law at Louvain, emerging with the title Maître, by which he was known from 1531. From 1558 he began styling himself Doctor of both laws. Where that doctorate came from, nobody has established. It is the first of many things about Taisnier that do not quite check out.

Singing for Charles V

The court was his making. From 1542 he was master of the school for the choirboys of the Imperial Chapel of Charles V, responsible for five students, and he described himself ever after as "sometime household chapel instructor and singer of his most puissant imperial majesty Charles V." He placed himself at Toledo in 1538, keeping Epiphany with the chapel singers, and claimed to have been at the Conquest of Tunis in 1535 — a claim scholars have traced only through secondary sources, never to a document.

He had a taste for the marvellous. At Toledo in 1538, he wrote, he watched a submersible vessel demonstrated on the Tagus, "where a lighted candle was carried under the waves" and came back to the surface still burning. In the *Opus Mathematicum* he announced that for the better part of his fifty-three years he had "travelled studiously through nearly the whole of Europe, and a great part of Africa, Asia and America." The America is doing a lot of work in that sentence.

A Wandering Lectureship

The verifiable career is impressive enough without the embroidery. He taught mathematics in the public academies of Rome in 1546–47 and at Ferrara in 1548. From 1549 to 1551 he was *phonascus*, vocal mentor, at the cathedral in Palermo, giving mathematics lessons on the side. He travelled Italy in the retinue of Cardinal Francisco Mendoza de Bobadilla, Bishop of Burgos, as his Director of Musicians, and came home around 1555. From 1555 to 1557 he ran a higher school at Lessines in Hainaut with five junior masters and more than four hundred pupils.

When Charles V surrendered power in the Netherlands in 1555, the ground shifted. By 1558 Taisnier had moved to Cologne, where he taught in the schools and the university and served as Kapellmeister to Jan Gebhardus, Archbishop-Elector of Cologne, who died in 1562.

The Four Quantities

Taisnier's programme was the medieval quadrivium restated with unusual conviction: a general theory of mathematics in four "Quantities" — astronomy, geometry, arithmetic and music — which, he argued in a dedicatory letter, "are so interrelated that any one of them remains imperfect without the other." A man who could teach the sphere and train cathedral singers was living proof of the thesis.

Cologne produced a burst of publication. *De Sphaerae Materialis Fabrica et Usu* (1558) was, characteristically, not a book but twenty-four pages of chapter headings for a projected work in eight books. *De Usu Spherae Materialis* (1559) delivered forty-six folios on the uses of the astronomical sphere. *De Annuli Sphaerici Fabrica et Usu* (Antwerp, 1560) covered the measurement of heights, distances, hours and artillery angles — the mathematics a gunner or surveyor needed. Alongside these ran the divinatory works: the *Astrologiae Iudiciariae Ysagogica* (1559), nearly two hundred folios justifying astrological prognostication and reading character from palm and face, and the *Opus Mathematicum octo libros complectens* (1562), of whose eight sections six are given to chiromancy and a seventh to physiognomy. The promised treatise on music, the subject he knew from the inside, never appeared.

Cologne, 1562: The Theft

The same year he published the *Opusculum perpetua memoria dignissimum, De natura magnetis et eius effectibus*. It is one of the most celebrated acts of plagiarism in the history of science.

The magnetic portion reproduces the *Epistola de magnete* of Peter of Maricourt, written around 1269 and printed in 1558 — the first serious experimental study of the lodestone in Europe. The section on perpetual motion and falling bodies reproduces Benedetti's *Demonstratio proportionum motuum localium* of 1554. Neither author is named anywhere. Taisnier dedicated the volume to his archbishop and let it stand as his own.

It is not pure theft. It contains original material on navigation, including how hull shape relates to a ship's speed and a long dissertation on the causes and sequence of the tides — the latter judged a definite step forward, because Taisnier correctly tied the tides to the motions of both sun and moon rather than the moon alone.

What the Theft Accomplished

Here the story turns strange. Taisnier's book circulated far more widely than either of the works it had swallowed. Around 1575 Richard Eden translated it into English as *A very necessarie and profitable booke concerning navigation* — the first text on magnetism in the English language. Kepler consulted Taisnier while developing his theory of a solar magnetic force. Benedetti's ideas on falling bodies, which anticipate Galileo, reached the Collegio Romano through this volume. Peregrinus's experimental method fed into William Gilbert's *De Magnete* of 1600.

Benedetti denounced the theft in 1574, questioning acidly how Taisnier could have understood material he lacked the capacity to grasp. But the plagiarism went largely unremarked in the wider literature until 1741, when Pierre Bayle's dictionary drew attention to it. For nearly two centuries, Europe read stolen goods and was the better for it.

Why Jean Is Called a Genius

The word has been used about him, but never cleanly. Lynn Thorndike, the historian of magic and experimental science, called Taisnier "a perplexing figure in whom a vein of intellectual dishonesty ran through the bedrock of his undoubted brilliance, usefulness and erudition." That formulation is the fairest available, and note what it concedes and what it withholds: brilliance and erudition, yes; originality, no.

The specific faculty Taisnier possessed was editorial rather than inventive. He read very widely across a fragmented Latin literature and had an unusually good eye for which obscure text mattered. Of everything available to a mid-century polymath, he chose to reprint Peregrinus on the magnet and Benedetti on falling bodies — two of the most consequential overlooked works of the century, one three hundred years old and one eight years old. Getting that judgement right twice, and packaging both for a working audience of navigators and gunners, is not nothing. The Belgian scholar Bosmans, while conceding Taisnier's "discomforting tendency towards self-promotion," argued that he was genuinely trying to synthesize and disseminate knowledge for students and practical use, and that loose attribution was not unusual in his century.

The counter-case is blunt. He announced books he never wrote. He spent his major work on palmistry. He claimed a doctorate nobody can locate and travels to America nobody believes. And he put his name on other men's discoveries. Whatever intelligence he had, it produced no idea that is his. Call him a superb transmitter with a talent for taste and a moral blind spot — that is the honest description, and it is not genius.

Legacy

He died in or soon after 1562, in Cologne; nothing certain is heard of him afterward, though dates as late as 1589 and 1595 have been proposed. An epitaph by Johannes Fontanus praised him as one who, living, "danced across the wandering stars." History's verdict is less lyrical and more useful: Jean Taisnier is remembered because he stole two books that deserved to be read, and made sure they were.