Robert Recorde, Inventor of the Equals Sign

David Nicholls via Flickr // CC BY-NC 2.0
David Nicholls via Flickr // CC BY-NC 2.0 / David Nicholls via Flickr // CC BY-NC 2.0

In the 16th century, British mathematics was somewhat lacking compared to other advanced nations in Europe. However, a doctor and math instructor named Robert Recorde did his best to equalize things, and invented one of the most important symbols in all of mathematics: the equals sign.

Recorde was born in Pembrokeshire, Wales, in 1510. Although there is scant knowledge regarding his youth, he reportedly “descended from a respectable family,” according to the 1911 Encyclopedia Britannica. He attended Oxford and Cambridge universities and then is believed to have taught at both venues before relocating to London, where he practiced medicine.

Some accounts hold that Recorde was a personal doctor to royalty, but this has been disputed. Either way, he authored a medical work called The Urinal of Physick, which instructed readers on how to make a diagnosis by observing a given sample of urine. Now an obsolete tract, it might be considered a minor classic in the genre of urological literature.

Of course, Recorde’s writing went far beyond urine. He also became a popular author of mathematical books. They were written in the English vernacular, as opposed to the Latin that most scholarly works (especially scientific and mathematical ones) were published in at the time. Writing for the Dictionary of Scientific Biography, Joy B. Easton tells how Recorde wrote “simple, clear English prose of a higher quality than his scientific contemporaries.”

His 1543 endeavor, The Ground of Artes, was, in its time, his most popular work. This book, which the author admittedly intended for “the symple ignorant” reader, focused on elementary arithmetic and included an added section to assist merchants in using the abacus. He later published the Pathwaie to Knowledge, which involved elementary geometry based on Euclid’s Elements.

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His following effort, The Castle of Knowledge, was a book on astronomy, which astutely included Nicolaus Copernicus’s new theory of heliocentricity, where the Earth revolved around the Sun, as opposed to the other way around, which had been the longstanding and ferociously maintained contention.

Recorde’s most famous book now is The Whetstone of Witte, which involved advanced arithmetic and algebra. This is the text where he introduces the equals symbol (=), which would forever change mathematics. His stated reason for choosing such a symbol was “bicause noe 2 thynges can be moare equalle.”

The Whetstone of Witte also saw the introduction of a term called “zenzizenzizenzic,” which was intended to represent a quantity raised to the eighth power. As Recorde wrote, zenzizenzizenzic “doeth represent the square of squares squaredly.” For rather obvious reasons, this clumsy term failed to catch on as well as the equals sign did. Even brilliant minds can be hit or miss.

In addition to math and medicine, Recorde was a fine scholar of classical and medieval documents. He also took part in governmental affairs, serving as a comptroller of the Bristol Mint. In this role, he encountered trouble, for he refused to divert currency to the future Earl of Pembroke. The Earl, incensed by the refusal, accused the mathematician of treason. Though Recorde would serve two months in captivity, he escaped with his head intact. But he was holding a serious grudge.

William Herbert, 1st Earl of Pembroke. Image credit: Museum of Wales via Wikipedia // Public Domain

In 1556, Recorde issued a formal charge of malfeasance against the Earl. In turn, the Earl appealed to Queen Mary and King Philip, who, judging that the Earl was far more important than a mathematician, made sure that the legal system would go its proper way.

However legitimate his grievance may have been, Recorde was injudicious in making the accusation. It is curious that such a bright man would engage in a pursuit so reckless. Apparently, his brightness was clouded by indignation.

On February 10, 1557, Recorde was fined £1000 for slander against the Earl. This was no small sum of money in the 16th century, and for Recorde it would prove an unsolvable problem. He eked out the remainder of his days at the King's Bench Prison in Southwark, London.

Dying at age 48, he left behind his intentions to write books on surveying and navigation. However, his existing books had become a staple of learning in Elizabethan England. Multiple generations of English scientists would credit Recorde with having elucidated mathematics for them.

About 100 years after his invention of the equals sign, the symbol had gained “general acceptance” in England, according to a Mathematics Teacher magazine article by Vera Sanford. By the 18th century, it had become standard in Europe.

But by writing in English instead of Latin, Recorde largely had sacrificed an international scholarly reputation. And he sacrificed his freedom by failing to acknowledge the privileged standing of the Earl—someone with whom he could never be equal.