Pope Leo IX in the context of Michael Cerularius

Several differences exist within the organizational structures and governance of the Catholic Church and the Eastern Orthodox Church. These are distinguished from theological differences which are differences in dogma and doctrine. A number of disagreements over matters of ecclesiology developed slowly between the Western and Eastern wings of the State church of the Roman Empire centered upon the cities of Rome (considered to have fallen in 476) and New Rome/Constantinople (also considered to have "fallen" in 1453) respectively. The disputes were a major factor in the formal East-West Schism between Pope Leo IX and Patriarch Michael I in 1054 and are largely still unresolved between the churches today.

Michael I of Constantinople (Cerularius or Keroularios; Greek: Μιχαὴλ Κηρουλάριος, romanized: Mikhaḗl Keroulários; c. 1000 – 21 January 1059) was the Ecumenical Patriarch of Constantinople from 1043 to 1059. His disputes with Pope Leo IX over church practices in the 11th century played a role in the events that led to the Great Schism in 1054.

Christianity in the 11th century is marked primarily by the Great Schism of the Church, which formally divided the State church of the Roman Empire into Eastern (Greek) and Western (Latin) branches.

In 1054, following the death of the Patriarch of Rome Leo IX, papal legates (representatives of the Pope) from Rome traveled to Constantinople to deny Michael Cerularius, the reigning Patriarch of Constantinople, the title of Ecumenical Patriarch and to insist that he recognize the Church of Rome's claim to be the head and mother of the churches. Cerularius refused, resulting in the leader of the contingent from Rome excommunicating Cerularius and the legates in turn being excommunicated by Constantinople. Though this event, in and of itself, was relatively insignificant (and the authority of the legates in their actions was dubious) it ultimately marked the end of any pretense of a union between the eastern and western branches of the Church. Though efforts were made at reconciliation at various times, they remained divided, either claiming to be the true Christian Church.

As distinct from abuse by some parish priests, who are subject to diocesan control, there has also been abuse by members of Roman Catholic orders, which often care for the sick or teach at school. Just as diocesan clergy have arranged parish transfers of abusive priests, abusive brothers in Catholic orders are sometimes transferred.

In response the Roman Catholic Church published its "Instruction Concerning the Criteria for the Discernment of Vocations with regard to Persons with Homosexual Tendencies in view of their Admission to the Seminary and to Holy Orders" in 2005. However this did not address the significant problem of heterosexual abuse by members of Roman Catholic orders.

Gerard (c. 1030 – 14 April 1070), also known as Gerard the Wonderful, was a Lotharingian nobleman. He was the count of Metz and Châtenois from 1047 to 1048, when his brother Duke Adalbert resigned them to him upon his becoming the Duke of Upper Lorraine. On Adalbert's death the next year, Gerard became duke, a position that he held until his death. In contemporary documents, he is called Gerard of Alsace (after the fact that he had some land in Alsace), Gerard of Chatenoy (after an ancestral castle near Neufchâteau), or Gerard of Flanders (after his wife's homeland).

He was the second son of Gerhard IV of Metz, count of Metz, and Gisela who was possibly a daughter of Theodoric I, Duke of Upper Lorraine. Henry III, Holy Roman Emperor, invested Adalbert with Lorraine in 1047 after confiscating it from Godfrey III. Godfrey did not back down, however, and killed Adalbert in battle. Henry subsequently bestowed it on Gerard, but the deposed duke continued to stir. Godfrey had the support of a faction of the nobles who did not want a strong hand at the ducal helm and Gerard was imprisoned. Gerard, however, had the support of the chiefest of his bishops, that of Toul, Bruno of Eguisheim-Dagsburg (later the sainted Pope Leo IX), who procured his liberation in 1049. The emperor gave him troops to assist him in his fight, for the rebels had the support of some elements in the church. Gerard himself remained, as his brother had, faithful to the end to the imperial dynasty and his descendants would remain so as well even into the Hohenstaufen years.

Pope Leo is the name of fourteen heads of the Catholic Church:

• Pope Leo I (the Great; saint; 440–461)
• Pope Leo II (saint; 682–683)
• Pope Leo III (saint; 795–816)
• Pope Leo IV (saint; 847–855)
• Pope Leo V (903)
• Pope Leo VI (928–929)
• Pope Leo VII (936–939)
• Pope Leo VIII (964–965)
• Pope Leo IX (saint; 1049–1054)
• Pope Leo X (1513–1521)
• Pope Leo XI (1605)
• Pope Leo XII (1823–1829)
• Pope Leo XIII (1878–1903)
• Pope Leo XIV (2025–present)