In the Nicene Creed, we profess, "I believe in one, holy, catholic, and apostolic Church": these are the four marks of the Church. They are inseparable and intrinsically linked to each other. Our Lord Himself in founding the Church marked it with these characteristics, which reflect its essential features and mission. Through the continued guidance of the Holy Spirit, the Church fulfills these marks.

First, the Church is one. The Catechism notes that the Church is one for three reasons: first, because of its source, which is the Holy Trinity, a perfect unity of three divine persons — Father, Son, and Holy Spirit; second, because of its founder, Jesus Christ, who came to reconcile all mankind through the blood of the cross; and third, because of its "soul," the Holy Spirit, who dwells in the souls of the faithful, who unites all of the faithful into one communion of believers, and who guides the Church (#813).

The "oneness" of the Church is also visible. As Catholics, we are united in our Creed and our other teachings, the celebration of the sacraments, and the hierarchical structure based on the apostolic succession preserved and handed on through the Sacrament of Holy Orders. For example, whether one attends Mass in Alexandria, Nigeria, Ghana, Togo, or wherever, the Mass is the same — the same readings, structure, prayers, and the like except for a difference in language — celebrated by the faithful who share the same Catholic beliefsand offered by a priest who is united to his bishop who is united to the Holy Father, the pope, the successor of St. Peter.

In our oneness, we do find diversity: The faithful bear witness to many different vocations and many different gifts, but work together to continue the mission of our Lord. The various cultures and traditions enrich our Church in their expressions of one faith. In all, charity must permeate the Church, for it is through charity that the members are bound together and work together in harmonious unity.

The Church is also holy. Our Lord Himself is the source of all holiness: "The one Christ is mediator and the way of salvation; he is present to us in His body which is the Church" (Dogmatic Constitution on the Church, #14). Christ sanctifies the Church, and in turn, through Him and with Him, the Church is His agent of sanctification.

 Through the ministry of the Church and the power of the Holy Spirit, our Lord pours forth abundant graces, especially through the sacraments. Therefore, through its teaching, prayer and worship, and good works, the Church is a visible sign of holiness.

Nevertheless, we must not forget that each of us as a member of the Church has been called to holiness. Through baptism, we have been freed from original sin, filled with sanctifying grace, plunged into the mystery of our Lord's passion, death, and resurrection, and incorporated into the Church, "the holy people of God." By God's grace, we strive for holiness.