Why do Catholics believe that their Church is the one true Church of Jesus Christ?

The Catholic Church possesses the four marks professed in the Creed: she is one, holy, catholic and apostolic.

One: The Catholic Church can be identified by a unity in the way she worships, the way she is structured, and in what she believes. The form of the liturgy is the same throughout the world. This unity is embodied as well through the structure of the hierarchy – each diocese has its bishop, and each bishop is under the authority of the Pope. The unified quality of the Catholic Church is perhaps best expressed by the beliefs that all Catholics profess during the Creed and the teachings that Catholics strive to follow.

Holy: We can say that the Church is holy because she brings the teachings of Christ to the world. The doctrines given to us by the Lord are the foundation of the Church. But above all, the Church is holy because she was established by Christ. In the Gospel of Matthew, Christ says to the Apostle Peter, “[Y]ou are Peter, and upon this rock I will build my church, and the gates of the netherworld shall not prevail against it. I will give you the keys to the kingdom of heaven. Whatever you bind on earth shall be bound in heaven; and whatever you loose on earth shall be loosed in heaven” (Matthew 18). In his own words, Christ established the Church, giving Peter the authority to represent him as his vicar on earth.

Apostolic: The Catholic Church can truly claim to be apostolic because she continues to look to the authority of the successor of Peter – the first Pope – and the bishops who are direct successors of the apostles. Christ promised to be with the apostles always, until the end of the world. In Scripture, we see that the apostles chose Matthias to be the successor of Judas. This succession has continued until the present day with the episcopal ordinations of bishops. Many other denominations were founded by a human being (Henry VIII, Martin Luther, Joseph Smith, etc.), but the Catholic Church today is the same Church that was founded by Jesus Christ and entrusted to the apostles.

Catholic: The word 'catholic' refers to the quality of universality; the Catholic Church is the same Church in the United States as in Scandinavia or Africa. As the world’s largest Christian denomination, the Catholic Church is not confined to a particular country, ethnic group, social class, or economic level. The Church is for everyone – Christ Himself instructed his followers to evangelize all nations.

There are other religions that may possess some of the qualities above, but only the Catholic Church can be considered the “one true Church” because she was founded by Christ, and is fully “one, holy, catholic, and apostolic.”