The Church traces its institution to Jesus and the Twelve Apostles, in particular Saint Peter, the leader of the Apostles, who is regarded as the first Pope. The first known use of the term "Catholic Church" was in a letter by Ignatius of Antioch in 107, who wrote: "Where the bishop appears, there let the people be, just as where Jesus Christ is, there is the Catholic Church."• Additionally, Catholic writers list a number of references which point to at least a 'first among equals' status for the See of Rome from the very earliest times.•

Central to the doctrines of the Catholic Church is Apostolic Succession, the belief that the bishops are the spiritual successors of the original twelve apostles, through the historically unbroken chain of consecration (see: Holy Orders). The New Testament contains warnings against teachings considered to be only masquerading as Christianity, and shows how reference was made to the leaders of the Church to decide what was true doctrine. The Catholic Church teaches that it is the continuation of those who remained faithful to the apostolic and episcopal leadership and rejected false teachings.

After an initial period of sporadic but intense persecution, Christianity was legalized in the fourth century, when Constantine I issued the Edict of Milan in 313. Constantine was instrumental in the convocation of the First Council of Nicea in 325, which sought to address the Arian heresy and formulated the Nicene Creed which is used by the Catholic Church, Eastern Orthodoxy, and various Protestant churches. On 27 February 380, Emperor Theodosius enacted a law establishing Catholic Christianity as the official state religion of the Roman empire.•


Following the decline of the Roman Empire, the Church underwent a time of missionary activity and expansion. The success of monasticism gave rise to various centers of learning, most famously in Ireland and Gaul, and contributed to the Carolingian Renaissance. Later in the medieval period, cathedral schools developed into Universities (see University of Paris, University of Oxford, and University of Bologna), the direct ancestors of modern Western institutions of learning.

During the 11th century, through a gradual process over a number of decades, the Church underwent the Great Schism in which the Catholic Church and Eastern Orthodoxy divided over a number of administrative, liturgical, and doctrinal issues, most notably the Filioque and papal primacy of jurisdiction. Both the Second Council of Lyons (1274) and the Council of Basel (1439) attempted to reunite the Churches, but in both cases the Orthodox rejected the councils. The Catholic Church and Eastern Orthodoxy remain in schism to the present day, although excommunications were lifted in 1965, and efforts to end the schism continue. Some Eastern churches have since been reunited with the Catholic Church, acknowledging the primacy of the pope, and together form the Eastern Catholic (sometimes referred to as "Uniate") Churches.


Beginning in 1092 the Crusades, a series of military campaigns, especially those in the Holy Land and sanctioned by the Papacy, began under the pontificate of Urban II in response to pleas from the Byzantine Emperor Alexis I for aid against Turkish expansion. The actions of the crusaders in this and subsequent crusades, such as the sacking of Constantinople in the Fourth Crusade, would become the subject of much controversy.

Beginning around 1184, and continuing through the Reformation, a number of historical movements involving the Catholic Church, broadly referred to as the Inquisition, were aimed at securing religious and doctrinal unity within Christianity through conversion, and sometimes persecution, of alleged heretics. A conviction of heresy, seen as treason against Christendom, could involve penalties ranging from a fine to a sentence of capital punishment such as burning at the stake. For an example of the rarity of this sentence, from 1540 to 1700 of all the cases brought before the Spanish Inquisition only 2-3% per year resulted in execution, lower than virtually any secular court of the time.• Historians distinguish between the Medieval Inquisition, the Spanish Inquisition, the Roman Inquisition, and Portuguese Inquisition as distinct historical events. The extent of the Inquisition's activity, and particularly the exact number of deaths, has been the subject of much subsequent propaganda.

The second great rift in the history of Christianity was the Protestant Reformation in the 16th century, in which various groups repudiated the primacy of the pope, various other Catholic doctrines and practices as well as abuses (such as simony) common at the time. Reformers within the Catholic Church launched the Counter Reformation, a period of doctrinal clarification, reform of the clergy and the liturgy, and re-evangelization begun by the Council of Trent.

The Council of Trent and its reforms provided the theme for the next 300 years of Catholic history. The period lay an emphasis on catechesis and missionary work, in which the Jesuit and Franciscan orders were prominent. Catholicism spread worldwide, at pace with European colonialism: to The Americas, Asia, Africa and Oceania. The 18th and 19th century Church found itself facing not only the teachings of Protestantism, but also Enlightenment and Modernist teachings about the nature of the human person, the state, and morality. With the coming of the Industrial Revolution, and the increased concern about the conditions of urban workers, 19th and 20th century popes issued encyclicals (notably Rerum Novarum) explicating Catholic Social Teaching.

The First Vatican Council (1869–1870) affirmed the doctrine of papal infallibility which Catholics hold to be in continuity with the history of Petrine supremacy in the Church, but Eastern Orthodox and Protestant churches consider it a theological innovation.

The Second Vatican Council (1962–1965) was convened by Pope John XXIII primarily as a pastoral but authoritative council, to make the historic teachings of the Catholic Church clear to the modern world. It issued documents on a number of topics, including the nature of the Church, the mission of the laity, and religious freedom. It also issued directions for a revision of the liturgy, the implementation of which resulted in, among other things, the celebration of Mass and the other sacraments in the living language of the people as well as in Latin, although some hold that the Council intended Latin to have priority.

Catholicism is monotheistic: it acknowledges that God is one, eternal, all-powerful (omnipotent), all-knowing (omniscient) and omnipresent (present in all places at all times). God exists as distinct from and prior to his creation (that is, everything which is not God, and which depends directly on him for existence) and yet is still present intimately in his creation. In the First Vatican Council the Church taught that, while by the natural light of human reason God can be known in his works as origin and end of all created things, God has also chosen to reveal himself and his will supernaturally in the ways indicated in the Letter to the .

Catholicism is also Trinitarian: it believes that, while God is one in nature, essence, and being, this one God exists in three divine persons, each identical with the one essence, whose only distinctions are in their relations to one another: the Father's relationship to the Son, the Son's relationship to the Father, and the relations of both to the Holy Spirit, constitute the one God as a Trinity.


A Catholic is baptized in the name (singular) of the Father and of the Son and of the Holy Spirit — not three gods, but one God subsisting in three Persons. While sharing in the one divine essence, the Father, Son, and Holy Spirit are distinct, not simply three "masks" or manifestations of one Person. The faith of the Church and of the individual Christian is based on a relationship with these three Persons of the one God.

The Catholic Church believes that God has revealed himself to humanity as Father to his only-begotten Son, who is in an eternal relationship with the Father: "No one knows the Son except the Father, just as no one knows the Father except the Son and those to whom the Son chooses to reveal Him."

Catholics believe that God the Son, the Divine Logos, the second of the three Persons of God, became incarnate as Jesus Christ, a human being, born of the Virgin Mary. He remained truly divine and was at the same time truly human. In what he said, and by how he lived, he taught all people how to live, and revealed God as Love, the giver of unmerited favours or Graces.

After Jesus' crucifixion and resurrection, his followers, foremost among them the Apostles, spread more and more extensively their faith with a vigour that they attributed to the presence of the Holy Spirit, the third of the three Persons of God, sent upon them by Jesus.

Unlike "families" or "federations" of Churches formed through the grant of mutual recognition by distinct ecclesial bodies, the Catholic Church considers itself a single Church ("one Body") composed of a multitude of local or particular Churches, each of which embodies the fullness of the one Catholic Church. The universal Church, however, is believed to be "a reality ontologically and temporally prior to every individual particular Church."•

However, the Catholic Church attaches great importance to the particular Churches within it, whose theological significance the Second Vatican Council highlighted. Two uses of the term particular Church are distinguished.

Autonomous (sui iuris) particular Churches or Rites. See: Eastern Rite Catholic Churches

Particular or local Churches (Dioceses and National Conferences of Bishops). See: Particular church

Bishops are assisted by priests and deacons. Parishes, whether territorial or person-based, within a diocese are normally in the charge of a priest, known as the parish priest or the pastor.

Priests may perform many functions not directly connected with ordinary pastoral activity, such as study, research, teaching or office work. They may also be rectors of churches or chaplains of communities or special groups. Other titles or functions held by priests include those of Archimandrite, Canon Secular or Regular, Chancellor, Chorbishop, Confessor, Dean of a Cathedral Chapter, Hieromonk, Prebendary, Precentor, etc.

In the Latin Rite or particular Church, only celibate men, as a rule, are ordained as priests, while the Eastern Rites, again as a rule, also ordain married men. Among the Eastern particular Churches, the Ethiopic Catholic Church ordains only celibate clergy, while also having married priests who were ordained in the Orthodox Church, while other Eastern Catholic Churches, which do ordain married men, do not have married priests in certain countries, such as the United States of America. The Western or Latin Rite does sometimes, but very rarely, ordain married men, usually Protestant clergy who have become Catholics. All Rites of the Catholic Church maintain the ancient tradition that, after ordination, marriage is not allowed. Even a married priest whose wife dies may not then marry again.

Within the Catholic Church, the Consecrated Life refers to the following: the Religious Life, eremitical life, consecrated virginity, societies of consecrated life and secular institutes. All of these are ways of Christian living by those who have made the prescribed public profession and vow that is recognized in Church Law.• Those who have made their profession and vow are not, however, part of the Church hierarchy, unless they are also ordained priests. They commit themselves, for the love of God, to observe as binding certain counsels from the Christian Gospel.
Most who feel called to following Christ in a more exacting way join what are called Religious Institutes,• often referred to in everyday life as religious orders or religious congregations, in which they follow a common rule under the leadership of a superior. They usually live in community, although some may for a shorter or longer time live the Religious Life as Hermits without ceasing to be a member of the Religious Institute.

Canons 603 and 604 give official recognition also to consecrated hermits and consecrated virgins who are not members of religious institutes (see below).

Many enlightenment philosophers perceived the Church's doctrines as superstitious and hindering the progress of civilization. In the most famous instance, many criticized it for the 1633 trial of Galileo Galilei, in which the Church condemned his advancement of the heliocentric system of Catholic priest Nicolaus Copernicus, in favour of a geocentric system. Pope John Paul II publicly apologized for the Church's actions in that trial on 31 October 1992. An abstract of the acts of the process against Galileo is available at the Vatican Secret Archives, which reproduces part of it on its website.

Recently, the Church is criticized for its opposition to scientific research in fields such as embryonic stem cell research, which the Church teaches would cause the utilitarian destruction of a human being, or simply put, an act of murder. The Church argues that advances in medicine can come without the destruction of human embryos; for example, in the use of adult or umbilical stem cells in place of embryonic stem cells.

Historians of science including non-Catholics such as J.L. Heilbron,• Alistair Cameron Crombie, David Lindberg,• Edward Grant, Thomas Goldstein,• and Ted Davis have been revising the common notion — the product of black legends say some — that the Church has had a negative influence in the development of civilization. They argue that not only did the monks save and cultivate the remnants of ancient civilization during the barbarian invasions, but the Church promoted learning and science through its sponsorship of many universities which, under its leadership, grew rapidly in Europe in the 11th and 12th centuries. St. Thomas Aquinas, the Church's "model theologian," not only argued that reason is in harmony with faith, he even recognized that reason can contribute to understanding revelation, and so encouraged intellectual development. • The Church's priest-scientists, many of whom were Jesuits, were the leading lights in astronomy, genetics, geomagnetism, meteorology, seismology, and solar physics, becoming the "fathers" of these sciences. It is important to remark names of important churchmen such as the Augustinian abbot Gregor Mendel (pioneer in the study of genetics) and Belgian priest Georges Lemaître (the first to propose the Big Bang theory).
Cardinal John Henry Newman used to say in the nineteenth century that those who attack the Church can only point to the Galileo case, which to many historians does not prove the Church's opposition to science since many of the churchmen at that time were encouraged by the Church to continue their research.•

While some critics accuse members of the Catholic Church of destroying the art of some of the colonized natives, several historians credit the Catholic Church for the brilliance and magnificence of Western art. They refer to the Church's fight against iconoclasm, a movement against visual representations of the divine, its insistence on building structures befitting worship, Augustine's repeated reference to (God "ordered all things by measure and number and weight") which led to the geometric constructions of Gothic architecture, the scholastics' coherent intellectual systems called the Summa Theologiae which influenced the intellectually consistent writings of Dante, its creation and sacramental theology which has developed a Catholic imagination influencing writers such as J. R. R. Tolkien• and William Shakespeare,• and lastly, the patronage of the Renaissance popes for the great works of Catholic artists such as Michelangelo, Raphael, Bernini, Borromini and Leonardo da Vinci.

The Catholic Church undertook one of the most comprehensive reforms in its history during the Second Vatican Council (1962–1965) and the decade which followed. For changes in the liturgy, see Mass of Paul VI. The Church stressed more than before what it saw as positive rather than what it saw as negative in other Christian communities, other religions, and the aspirations of human beings in general. It encouraged the up-to-date renewal of religious life. And it empowered episcopal conferences to enact adaptations in disciplines such as abstinence from meat on Fridays.

Some Catholics, who have become known as traditionalist Catholics, rejected many of these changes, which they viewed as inconsistent with what the Church had always taught. Among the most controversial of changes was the adoption of a new rite of Mass, which traditionalist Catholics view as watered down, "protestantized", or even invalid.

The Catholic Church teaches that human life and human sexuality are both inseparable and sacred. Some criticize the Church's teaching on sexual and reproductive matters. The Church requires members to eschew masturbation, fornication, pornography, prostitution, rape, homosexual practices, and artificial contraception. The procurement or assistance in abortion can carry the penalty of excommunication, as a specific offence.


Some criticize the Church's teaching on fidelity, sexual abstinence and its opposition to promoting the use of condoms as a strategy to prevent the spread of HIV/AIDS, teen pregnancy, and STDs as counterproductive. However, the Church maintains that the promotion of abstinence is the only effective way to deal with the AIDS crisis.

Cardinal Javier Lozano Barragán, President of the Pontifical Council for Pastoral Assistance to Health Care Workers, has stated that Pope Benedict XVI asked his department to study the issue as part of a broad look at several questions of bioethics.• However, the president of the Pontifical Council for the Family, Cardinal Alfonso López Trujillo, in an interview reported by Catholic News Agency on May 4, 2006, said that the Church "maintains unmodified the teaching on condoms", and added that the Pope had "not ordered any studies about modifying the prohibition on condom use."•