If we refer back to the first paragraph and the analogy we make about "Womb to Tomb" we can see this sacrament as the sacrament of spiritual birth. It is not the belief of the Catholic church that children are born as sinful people. Rather they are seen as being born into a sinful state. Christian baptism is the means God has chosen to help his children to tread through the rather murky waters of a sinful, selfish and godless world.
The Long View
The word "baptism" comes from the Greek word baptizein which means to plunge or immerse. It has its origins in Judaism, which required converts to undergo a bath of purification as Jesus did when He was baptized by John in the River Jordan, after which He began His public life. After His death and resurrection, He told His disciples: "Go therefore and make disciples of all nations, baptizing them in the Holy Spirit, teaching them to observe all that I have commanded you." (Matthew 28:19-20) Throughout history the Church has followed Jesus' command, instructing those who desire to become Christians and then baptizing them in the name of the Father and of the Son and of the Holy Spirit.
Baptism marks the entry of the believer into the Christian community. Along with Confirmation and Eucharist, it is one of the Sacraments of Initiation, giving access to the full sacramental life of the Church. Through Baptism we are freed from sin and joined with Christ, sharing in His divinity and destined for eternal life. Baptism leaves us permanently changed, no longer the person we once were, but a new person, dying to death and sin, and rising to new life in Christ. In the words of St. Paul, "We were buried with Him through baptism into death in order that, just as Christ was raised from the dead through the glory of the Father, so too may we live a new life." (Romans 6:4)
In ancient baptismal rites catechumens were dramatically plunged into large cisterns of water and, while the celebrant said the Trinitarian formula, "I baptize you, in the name of the Father, and of the Son and of the Holy Spirit," immersed three times to signify their death to sin and resurrection to new life. Since the reforms of Vatican II there are three separate baptismal rites: one for infants; one for children old enough to understand; and one for adults.
The essential part of the rite is unchanged, consisting of pouring water over the head while saying the Trinitarian formula. Anyone can baptize in an emergency, although the usual minister of the sacrament is a priest or deacon. Usually the rite includes anointing the forehead with holy oil to indicate that, even as Christ was anointed Priest, Prophet, and King, so does the candidate now share in His everlasting life, participating in His glory as a member of His body. The newly baptized then receives a white garment and a candle lit from the paschal candle. Like Christ, who is the light of the world, the newly baptized Christian carries the light of Christ out into the world.
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Next Sacrament: Confirmation