Johannes de Sacrobosco

Johannes de Sacrobosco, also written Ioannis de Sacro Bosco (c. 1195 – c. 1256), was a scholar, monk and astronomer who was a teacher at the University of Paris. He wrote a short introduction to the Hindu–Arabic numeral system which became the most widely read introduction to that subject in the later medieval centuries (judging from the number of manuscript copies that survive today). He also wrote a short astronomy textbook, Tractatus de Sphaera, which was widely read and influential in Europe during the later medieval centuries as an introduction to astronomy. In his longest and most original book, Sacrobosco correctly described the defects of the then-used Julian calendar, and, three centuries before its implementation, recommended a solution much like the modern Gregorian calendar.

Very little is known about the education and biography of Sacrobosco. For one thing, his year of death has been guessed at 1236, 1244 and 1256, each with plausibility and each with lack of adequate evidence.

The country in which he was born is uncertain. In year 1271 Robertus Anglicus stated that Sacrobosco was born in England. That could be true, yet there is neither good supporting nor good contradicting evidence for it. On the basis of the testimony of someone writing in year 1271, a birthplace in England can be taken as having more likelihood than other possibilities. Among other possibilities, several different tenuous efforts have been made to figure out his birthplace from his appellative de Sacrobosco. Long after his death, Johannes de Sacrobosco was called and sometimes still is called by the name John of Holywood or John of Holybush, a name which was constructed by post-hoc reverse translation of the Latin sacro bosco, where sacro = "holy" (sacred), and bosco = "wood". "Sacrobosco" as such is an unknown town or region. One traditional report, that he was born in Halifax, West Yorkshire, is due to a 16th-century author, John Leland, and was discredited by William Camden: Halifax means 'holy hair', not 'holy wood'. Sacrobosco has been identified, by Thomas Dempster, with an Augustinian canon from Holywood Abbey, Nithsdale (in fact a Premonstratensian house); which would be a reason for imagining him to have been born in Scotland. He is also claimed by Holywood, County Down, this being based on a suggestion of Richard Stanihurst. However, Pederson attributes this assertion to Holywood being known to Stanihurst. Pederson's book mentioned that in 1639 James Ware assumed that the birthplace of Sacrobosco was near Dublin. Stanihurst and even Pederson were probably unaware that the seat of the Sacrobosco/Hollywood family in Ireland was in Artane, a suburb of Dublin ("The History of the County of Dublin" by John D'Alton published in 1838). Local historical records in Ireland seem to indicate that Sacrobosco was a member of the Artane Hollywoods and was born in Artane Castle. A similar claim is made for Holywood, County Wicklow, though there is no known historical document which supports this.

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