Catholicism is the largest denomination within Christianity with approximately 1.2 billion people being members of the assembled body of Catholic believers, the Roman Catholic Church. An individual can become a member of the Catholic Church through Rite of Christian Initiation of Adults.

Pope Francis, bishop of Rome and leader of the Roman Catholic Church


In common with other Christian communities the Roman Catholic Church professes belief in one God (monotheism), who is one in being but tripersonal, that is, eternally subsists as the three distinct persons of the Trinity: the Father, the Son and the Holy Spirit. The three divine Persons of the Trinity are considered distinct but completely equal in all things, since they are of but one essence and constitute the one God. God is believed to be, among other attributes, eternal (uncreated), infinite and spiritual (not physical), transcendent (above all things), ineffable (unlike anything), omnipotent (all-powerful), omniscient (all-knowing) and the Creator of all things.

Jesus Christ

Central to Christianity in general, and thus to Catholicism, is the figure of Jesus Christ, the Son of God. Jesus Christ is believed to be the Second Person of the Trinity (the Son or the Word of God) become man (which phenomena is known as the Incarnation), so that he is at once both fully God and fully human—one divine person with two natures: one divine and eternal, and one human, joined forever at the Incarnation. Jesus Christ is believed to have been miraculously born of a Virgin, the Virgin Mary. Catholics give to Mary the honorific title 'Mother of God' (or Greek Theotokos 'God-bearer') because she gave birth not to a mere man, but God in the flesh.

It is after Jesus Christ that all Christians are called 'Christian' (Jesus being the promised/prophesied 'Anointed One' [Χριστός/Christos in Greek] promised by God in the Old Testament). Equally definitional to Christianity is the belief that Jesus Christ gave His life freely in His suffering and subsequent death by crucifixion (called the Passion) to redeem mankind from their sin (called the Redemption). Since Jesus is the Redeemer of a people for God from their sins, He is called the 'Savior'.


The need for a Savior comes from the belief in Original Sin, referring both to the first sin committed when Adam, the first man ever created, being the representative of the human race, sinned against God's direct and explicit wishes, and also to the fallen state in which all his offspring, the human race are consequently born; that is, with a deficient nature prone to sin, technically a curse prescribed by God before the first sin was committed.

Catholics, along with other Christians, reject the idea that man can 'fix' this problem of sin on his own, teaching that only God can provide a solution, namely Jesus Christ, the Redeemer of the human race, who Catholics must believe is the only means of salvation (Jn 14:6). That is, man has no natural initiative or capability of salvation from sin unless God moves them by His grace to spiritual regeneration, found in Baptism. However, Catholics also reject the view that man is totally unable to co-operate with the grace or spiritual gifts of God once regenerated by Him, in order to be saved, and believe that man has free will.

Origins of the Church

St. Paul's statue which stands outside St. Peter's Basilica, Vatican City, Rome—the headquarters of the Roman Catholic Church.

The Catholic Church traces back its origins to the ministry of Jesus in the first century AD, and to the teaching of His disciples and His twelve closest disciples, the (Twelve) Apostles. Catholics believe that the Church was founded directly by Jesus Christ (Matt 16:18), principally through the teaching and ministry of His Apostles, as well as the seventy disciples, who founded the various local Christian communities (churches) which make up the Church as a whole.

Although Jesus is said to have ordained all of His Apostles as bishops or appointed 'overseers' in the Church, Catholics believe that Jesus made St. Peter, one of Twelve Apostles, the head or leader of the Church on earth, His vicar or steward, known as the Pope. The Pope is simply the title of the Bishop of Rome, who holds the office of the Papacy. Apostolic Succession refers to permanency and validity of the succession of bishops to their successors, ultimately from the Apostles themselves, by the laying on of hands in ordination.

The Deposit of Faith

Holy Scripture

Catholicism, like other Christian denominations, posits the belief in the Bible, comprised of an Old and New Testament as the divinely inspired (θεόπνευστος/theopneustos 'God-breathed' 2 Tim 3:16) written Word of God. Inspiration meaning that the Holy Spirit, God, guided and directly influenced the writing of Scripture in such a way as to produce an infallible and inerrant record of truth.

Sacred Tradition

In addition to the written Word of God, the Scriptures (the Bible), and to what other Christians believe, Catholics also adhere to Sacred Tradition (also called Apostolic Tradition), which is the 'living memory' of the Church of those teachings and practices handed on by the Apostles to the Church not written in Scripture, but which hold just as much authority for the believer as the written, since they have the same origin in the Apostles and ultimately God.

These two 'veins' of divine revelation constitute what is known as the deposit of faith, and its authentic interpretation is the prerogative of the Church, not the private individual. This authoritative teaching body (consisting of the bishops of the Church in union with the Pope), is called the Magisterium.

The Seven Sacraments

The Catholic Church has seven sacraments or rituals it holds where instituted by Jesus, and through which divine grace is conferred through outward signs. Namely, Baptism, Confirmation, Eucharist (Holy Communion), Reconciliation (Confession), Anointing of the Sick (Extreme Unction), Holy Matrimony (Marriage), and Holy Orders (Ordination). Not all sacraments are necessary for all believers (such as ordination into the priesthood) and not all are received, but the Church teaches that Baptism is absolutely necessary for salvation (regeneration from the state of original sin, which it effaces from the soul), and the Eucharist, the replenishment and life of the soul through which the faithful live in and because of Christ.


The most important and defining sacrament in Catholic theology and liturgical practice is the Sacrament of the Eucharist. The Eucharist is the central element of the Holy Mass, the Roman Catholic service of worship, and is presented in the form of bread and wine through consecration by the priest. In common with most Eastern churches, Lutheranism and some strands of Anglicanism, and in contrast to Calvinism and the remaining strands of Anglicanism, Catholics consider the bread to be the real body of Christ and the wine to be the real blood of Christ. Whereas the Eastern churches have no specific doctrine with respect to the Eucharist and Lutheranism holds that bread and wine are present in addition to the body and blood of Christ (consubstantiation), Catholicism believes that the substance of bread and wine are transformed into the body and blood of Christ, whilst the outward forms are still visible as bread and wine (transubstantiation).

The bread and wine are transformed into the real Body and Blood of Jesus at the words of consecration by the priest, who offers it as an 'unbloody' representation of Christ's once-for-all sacrifice on the Cross, to God the Father on behalf of and for the sins of the world. This act of the change of substance from bread and wine into the body and blood of Christ is called transubstantiation, after which the essence of bread and wine no longer remain, except only in appearance. The Holy Sacrifice of the Mass (usually called simply the Mass) is definitional to the faith, and is the heart and center of the Church's worship. This is in contradistinction to some Protestant Christians, such as Lutherans, who believe that Christ is merely present 'with' and not in the elements of the bread and wine, and others still who hold that the Eucharist is merely a reminder and commemoration of the Last Supper, rather than sacrificial in nature. The doctrine that Christ is truly and substantially present in the Eucharist, under the appearance of the bread and wine, is called the Real Presence.

The Communion of the Saints

Though not a feature unique to Catholicism, belief in saints and their intercession with God on behalf of the faithful is a prominent feature of personal devotions and public worship (although saints are not themselves the object of worship). Communion of the saints refers to the spiritual communion that the living and the departed in Christ have. Catholics, unlike Protestants, believe that the saints can intercede and hear our prayers, which they can then offer to God from a more favorable position in heaven, as the "righteous made perfect" (Heb 12:23). Of the saints, the Blessed Virgin Mary, the mother of Christ, as the Mother of the 'God-man', is the most prominent of the saints, and is believed by Catholics (as a matter of faith, called a dogma, which must be believed) to have been preserved from all sin, including original sin, given her role as the mother of God, who is all-holy. Thus Mary has a special place in the devotions and prayers of the Catholic faithful.

The rest of the book will treat the practices, sacraments and doctrines of Catholicism in more detail.

Catholics come to adore the consecrated Eucharist exposed for adoration on the altar (center).

The rest of the book will treat the practices, sacraments and doctrines of Catholicism in more detail.