Jean Leurechon

Jean Leurechon (c. 1591 – 17 January 1670) was a French Jesuit priest, astronomer, and mathematician, known for inventing the pigeonhole principle and naming the thermometer.

Leurechon was born in Bar-le-Duc where his father, also named Jean Leurechon, was a physician to the Duke of Lorraine.^[1] He sent Leurechon to be educated at the Jesuit university in Pont-à-Mousson but, learning of Leurechon's desire to take holy orders^[2] and wishing him instead to become a physician,^[1] brought him back to Bar-le-Duc.^[2] In 1609 Leurechon ran away from home to return to the Jesuits,^[2][3] and the story goes that this so enraged his mother that she took up a dagger and attempted to assassinate the head of the local Jesuit order.^[3] His father appealed to the parliament in Paris, which had jurisdiction over Pont-à-Mousson, and Leurechon was returned again to Bar-le-Duc, where the Duke ordered Leurechon to be held at the convent of the Minims in Nancy.^[3][2] This did not change his resolve, and after a month his parents let him go.^[3]

Leurechon taught mathematics from 1614 to 1629 at Pont-à-Mousson,^[4] and in 1631 became rector of the Collège Gilles de Trèves [fr], a Jesuit school in Bar-le-Duc.^[1][3] This position reconciled him with his parents, who willed their estate to the Jesuits.^[3] At Bar-le-Duc, he also took the confessions of Charles IV, Duke of Lorraine.^[2]

From 1649 to 1655 he worked in an army chapel in Brussels.^[5] He died on 17 January 1670 in Pont-à-Mousson.^[2]

After two earlier works on astronomy,^[6] in 1619 Leurechon published two works on a comet that became visible in November and December of 1618.^[7] In 1622 he published the book Selectæ Propositiones in Tota Sparsim Mathematica Pulcherrimæ.^[4] Another book, Récréations Mathématiques, concerning recreational mathematics, was published in 1624 at Pont-à-Mousson under the name H. van Etten, described in the dedication of the book as a student at Pont-à-Mousson. It has been commonly attributed to Leurechon, and the van Etten name interpreted either as a pseudonym or as a "modest" misattribution, but this has been disputed by some scholars, who argue that an actual student named van Etten was the author.^[4][5][8][9] It was republished in many later editions.^[5]

The 1622 book contained a brief reference to the pigeonhole principle, much earlier than its common attribution to Peter Gustav Lejeune Dirichlet in 1834, and the 1624 book spelled out the principle in more detail.^[4] The 1624 book also contained the first use of the word "thermometer", replacing an earlier word "thermoscope" for the same device.^[9][10]