Petrus (Peter) Comestor was a French theological writer (died c. 1178).
Born in Troyes, he was first attached to the Church of Notre-Dame in that city and habitually signed himself as "Presbyter Trecensis". Before 1148 he became dean of the chapter and received a benefice in 1148. About 1160 he formed one of the Chapter of Notre-Dame at Paris, and about the same year he replaced Eudes (Odon) as chancellor. At the same time he had charge of the theological school.
It was at Paris that Peter Comestor composed and certainly finished his Historia Scholastica; he dedicated it to the Bishop of Sens, Guillaume aux Blanches Mains (1169–76). Pope Alexander III ordered Cardinal Peter of St. Chrysogonus to allow the chancellor Peter to exact a small fee on conferring the licence to teach, but this authorization was altogether personal. A short time afterwards the same cardinal mentioned the name of Peter to Alexander III, as among the three most cultured men of France.
The surname of "Comestor" ("devourer"), given to Peter during his life, also demonstrates the esteem in which his learning was held: he was a great bookworm. He often refers to his surname in his sermons and in the epitaph said to be composed by him: "Petrus eram ... dictusque comestor, nunc comedor." ("Peter was I... and called the devourer: now I am eaten.") He afterwards withdrew to St. Victor's Abbey, Paris and made profession of canonical life.
Petrus Comestor died in Paris around 1178. He was buried at St. Victor's, and the necrology of the canons mentions him as one of themselves (21 October).
His Historia Scholastica is a kind of sacred history composed for students. The author begins the sacred narrative at the Creation, and continues it to the end of the incidents related in the Acts of the Apostles; all the books of the Bible are contained therein, except those whose nature is purely didactic, the Book of Wisdom, the Psalms, the Prophets, the Epistles, etc. The discourses are abbreviated.
He borrows frequently from profane authors, especially from Flavius Josephus for the beginning of the Gospels, and very often the test is as though paraphrased in a commentary where all data, cosmological and physical, philosophical, theological, geographical, etc., are found. There are numerous inaccuracies and fables. The work consists of twenty books and often small "additions" supply geographical or etymological appendixes at the end of the chapters. This Biblical history met with great success, as witness the large number of manuscripts, the mention of his name in all the libraries of the Middle Ages, the lists of classical books for the universities and schools, the quotations and the eulogies with which the name of its author is everywhere accompanied (cf. the canonist Huguccio, about 1190) and its numerous translations, most of all the Bible Historiale in French. In the fifteenth century, the work was still in great demand, as can be seen by the editions made before 1500 of the Latin text, or of the French translation. Migne  reproduces the Madrid edition of 1699.
The sermons of Peter Comestor have been left to us in numerous manuscripts, often under other names, but the complete and continued series has not yet been published. A series of fifty-one sermons was placed wrongly under the name of Peter of Blois and printed among his works; some figure also in the works of Hildebert de Mans. The sermon in which the word "transubstantiation" occurs, the 93rd (not 73rd), is not Hildebert's but Peter Comestor's; the word however is already found in Roland Bandinelli (the later Pope Alexander III) before 1150.
Other collections, like that of the 114 sermons copied at St. Victor before 1186, are still unpublished, more than twelve manuscripts are in the libraries of Paris, and all has not yet been unravelled in this assortment. As a preacher, Peter was subtle and pedantic in his style, in keeping with the taste of his time and of his audience of scholars and professors assembled around the pulpit of the chancellor. The sermons attributed to him during his stay at St. Victor are simple in style, instructive, and natural in tone. Also some verses are attributed to Peter Comestor and a collection of maxims entitled Pancrisis, perhaps that which still exists in a manuscript of Troyes.
- Strasburg, 1469, 1483, 1485, 1847; Reutlingen, 1473; Lyons, 1478; Basle, 1486; Paris 1487, etc.
- Patrologia Latina CXCVIII, 1053-1844.
- Migne, CCVII, and CCVIII, 1721, etc.
- Migne, CLXXI, sermon, 7, 15, 17, 21, 22, 23, etc.
- Petris Comestoris Scolastica Historia: Liber Genesis. Edited by Agneta Sylwan. Turnhout: Brepols, 2004, Pp. xc + 227. (Corpus Christianorum Continuatio Mediaevalis, 191).