The doctrine of the Roman Catholic Church on this matter is that, while, in Jesus himself affirms that baptism is necessary for salvation, the effects of sacramental baptism are brought about also by "Baptism of blood" (dying for the sake of the faith) and "Baptism of desire", whether explicit, as in the case of catechumens, or implicit, as in the case of anyone who is ignorant of the Gospel of Christ and of his Church, but seeks the truth and does the will of God in accordance with his understanding of it, while, as regards children who die without baptism, the Church entrusts them to the mercy of God. In Catholic teaching, baptism, like all the sacraments, presupposes faith and by words and objects also nourishes, strengthens, and expresses it. "Baptism is the sacrament of faith (cf. Mark 16:16). But faith needs the community of believers. It is only within the faith of the Church that each of the faithful can believe. The faith required for Baptism is not a perfect and mature faith, but a beginning that is called to develop.
Baptismal regeneration is held to be heretical by Reformed churches. Leonard Feeney's propounding the view that water baptism is absolutely necessary for salvation brought him into conflict with the Catholic Church.
Scriptures such as and are used by proponents to support this teaching.
Opponents often cite the account of where Jesus, when on the cross, said to one of the thieves crucified with him, "Today, you shall be with me in paradise," although there is no record that he had been baptized. Proponents allege that, before Jesus' death on the cross, he did at times forgive sins for differing reasons and with differing actions on the part of the one forgiven (cf. , ) but, since his death, one must be united with him through baptism (). Naturally, this argument is rejected by Christians who believe that God has always saved people by the same means for the same reason.