Why Only One Baptism in the Catholic Church?

There is one baptism because there is only person, our Lord Jesus Christ, who was capable of atoning for the sins of mankind, something a mere man could not do. Baptism applies the merits of Christ’s one Sacrifice of Calvary, his Paschal Mystery (CCC 1085), so that we can be forgiven of our sins and become temples of the Holy Spirit (CCC 1262ff.).

Baptism consequently makes us one in Christ (see 1 Cor. 12:12-26), whereas a number of baptisms would suggest disunity among God’s people. And so St. Paul can say with Christ-centered pride in Ephesians 4:1-6:

I therefore, a prisoner for the Lord, beg you to lead a life worthy of the calling to which you have been called, with all lowliness and meekness, with patience, forbearing one another in love, eager to maintain the unity of the Spirit in the bond of peace. There is one body and one Spirit, just as you were called to the one hope that belongs to your call, one Lord, one faith, one baptism, one God and Father of us all, who is above all and through all and in all.