Peckham studied at the University of Paris under Bonaventure, where he later taught theology and became known as a conservative opponent of Thomas Aquinas, especially regarding the nature of the soul.

As archbishop, Peckham oversaw attempts to close down Jewish synagogues, punish relapsing Jews from "returning to their vomit", and associating with Christians.

[3] In the field of optics, Peckham was influenced by Euclid, Pseudo-Euclid, Aristotle, Augustine, al-Kindi, Avicenna, Alhazen, Grosseteste, and Roger Bacon.

[10] He did not long remain in that post, being summoned to Rome as lector sacri palatii, or theological lecturer at the papal palace.

[11] It is likely that he composed his Expositio super Regulam Fratrum Minorum, a work that included information on preaching, a subject that Peckham felt was of great importance.

[12] In 1279 he was appointed Archbishop of Canterbury by Pope Nicholas III who had prohibited the election of Robert Burnell, Edward I's preferred candidate.

His first episcopal act was calling a council at Reading in July 1279 to implement ecclesiastical reform, but Peckham's specifying that a copy of Magna Carta should be hung in all cathedral and collegiate churches offended the king as an unnecessary intrusion into political affairs.

[18] Notwithstanding his other actions, Peckham's relations with the king were generally good, and Edward sent him on a diplomatic mission to Llywelyn ap Gruffudd in Wales.

He also found the Welsh clergy to be uneducated, although he did order a Welsh-speaking suffragan bishop to be appointed to help with pastoral duties in the diocese of Coventry and Lichfield.

[22] As part of his diplomatic duties, Peckham wrote to Llywelyn, and in those letters the archbishop continued his criticisms of the Welsh people, this time condemning their laws as contrary to both the Old and New Testament.

[27] He also forbade an effort by the Benedictine order in England to reform their monastic rule, to allow more time for study and for more education for the monks.

[28] At an ecclesiastical council held at Lambeth in 1281, Peckham ordered the clergy to instruct their congregations in doctrine at least four times a year.

They were to explain and teach the Articles of Faith, the Ten Commandments, the Works of Mercy, the Seven Deadly Sins, the Seven Virtues and the Sacraments.

[31] The constitutions, which were originally in Latin, were the basis and inspiration for pastoral and devotional works throughout the remainder of the Middle Ages, and were eventually translated into English in the 15th century.

[36] He once wrote to Roger de Meyland, the Bishop of Coventry and Lichfield "These things need your attention, but you have been absent so long that you seem not to care.

These strains between the archbishop and his subordinates were intensified by clashes over ecclesiastical and secular authority, as well as Edward's great need for income.

[40] On hearing that the Jews of London were being allowed to build a new Synagogue, "to the confusion of the Christian religion" Peckham lobbied to stop it.

[43] Peckham also clashed with Queen Eleanor stating to her that her use of loans from Jewish moneylenders to acquire lands was usury and a mortal sin.

"[45][b] In Easter 1285, the prelates, (senior church leaders) of the Province of Canterbury under Peckham's leadership drew up complaints to Edward, two of which were regarding what they saw as lax restrictions on Jews.

They complained about converts lapsing back to Judaism, and called for a crack down on usury, which although banned since 1275 under the Statute of the Jewry, they believed was still being practiced, asking that "the Jews' fraud and malice be vigorously opposed".

[46] These concerns were reiterated directly to Peckham in a letter from the Pope Honorius IV, in November 1286, which Peckham and other church leaders used as guidance to make further calls against the Jews in the 1287 Synod of Exeter, again demanding the wearing of Jewish badges, banning Christians from working for Jews, from sharing meals with them, or using Jewish doctors.

[51] A number of his works have survived, and some have appeared in print in various times: Peckham is the earliest Archbishop of Canterbury to have his registers, the principal records of archiepiscopal administration, held at Lambeth Palace Library.