Contributions
Born at Tenby, in south Wales, and educated at Oxford and then Cambridge in medicine, Robert Recorde achieved a quiet but decisive revolution: he wrote mathematics in English, at a time when learning was passed on in Latin. His series of textbooks, cast as dialogues between a master and his pupil, made arithmetic, geometry and astronomy accessible to merchants, artisans and sailors. "The Grounde of Artes" (1543) teaches calculation; "The Pathway to Knowledg" (1551) gives the first Euclidean geometry in English; "The Castle of Knowledge" (1556) sets out astronomy and presents the Copernican system with favour; and "The Whetstone of Witte" (1557) introduces algebra and, with it, two lasting innovations: the "plus" and "minus" signs to the English public, and above all the invention of the equals sign "=", which he drew as a pair of parallel lines, "because no two things can be more equal."
Significance
Recorde is the father of English mathematics and one of the great popularisers of science in the whole Renaissance. His audacity was linguistic and democratic: by choosing English over the Latin of the learned, he wrested calculation from the circle of clerks and placed it in the hands of those who had concrete use for it, the merchants and navigators of a kingdom in full maritime expansion. His lively, teacherly dialogue form made his books bestsellers reprinted for more than a century, schooling generations of Englishmen in number. His invention of the "=" sign is one of those tiny finds that change the face of a discipline: adopted the world over, the symbol is today among the most universal in human thought, and it came from the pen of a Welshman. Recorde also dared, in a still cautious country, to praise Copernicus. But his life ended in misfortune: engaged in the administration of the royal mines and mints, he fell out with a powerful man, the Earl of Pembroke, was prosecuted, condemned for debt and died in prison, in the King's Bench, around June 1558. The founder of English mathematics ended ruined, victim of the quarrels of power as much as of his own uncompromising temper.
Influence
His textbooks schooled generations of Englishmen in calculation and were reprinted for more than a century; he gave the English language its mathematical vocabulary. His invention of the "=" sign became universal. By spreading Euclidean geometry and the Copernican system in English, he prepared the ground for English science of the seventeenth century. Recorde drank in the mathematical humanism of the Renaissance and the great ancient texts, Euclid foremost, which he set out to transmit in the vernacular; the cosmological debates of his time and the recent reading of Copernicus shaped his astronomy, and the pedagogical tradition of the dialogue gave him his form.
Anecdote
It is in the closing pages of his algebra treatise, "The Whetstone of Witte" (1557), that Recorde performed his most lasting act. Weary, he writes, of endlessly repeating the words "is equal to," he decided to replace them with a symbol: a pair of parallel lines of the same length, "because no two things can be more equal" than two twin straight lines. Thus was born, almost for the convenience of writing, the "=" sign that the whole world uses today. The man died ruined in prison the following year, unaware that he had just given humanity one of its most universal symbols.