Baptism is the sacrament that frees man from original sin and from personal guilt, that makes him a member of Christ and His Church. It is thus the door to a new and supernatural life.

This sacrament has been undisputed in the Church since the beginning of Christian tradition. It has never been rejected by any heresy intending to remain on a Christian basis. Doubts could arise only about the ways and means of administering it and on its effects and way of operation. These things are therefore in essence what Church documents about baptism deal with.

The Church teaches:
Baptism is a true sacrament instituted by Christ. It is administered by washing with natural water and at the same time invoking the Most Holy Trinity. Anybody, even an unbeliever or a heretic can validly administer baptism. Since it confers grace by the signs' being properly carried out children can and should be baptized even while still infants. Baptism is necessary for salvation. Baptism effects the remission of original sin and actual sins and of all punishment due to sin; it confers sanctifying grace, membership in Christ and in the Church and the obligation to obey the Church's laws, and give an indelible character.

Note: from Pope Innocent III AD1201. The baptism of young children is not profitless. As circumcision made men members of the People of Israel, so baptism gives them entry to the kingdom of heaven.