In this course, we are going to explore the mystery of the Church in order to understand what it means to be part of her. We will look at the history of Church in Sacred Scripture, the mystery of the Church in time and eternity, and your life in the Church today. Through it all, the goal is not only to deepen your understanding of the Church but also to strengthen your appreciation for the Church, helping you to recognize more clearly that the Church is an indispensable gift through which God seeks to unite you ever more closely to himself.

The greatness of the Church’s mystery is one of the reasons God has given us a wide array of images to help us understand the Church. Each image is a metaphor that helps us to see a particular aspect of the Church. In a sense, each image is like a window through which we can gaze upon the truth. The wide variety of images of the Church is because the truth of the Church is inexhaustible.

The Nicene Creed that we pray every Sunday at Mass states that we believe in “one, holy, catholic, and apostolic Church.” These characteristics of the Church are called the four “marks of the Church.” They tell us that the true Church is one. She is holy. She is catholic (which means “universal”). And she is apostolic. The Church can be recognized by these four characteristics.

The Church is both the sign of humanity’s communion with God and the instrument that makes that communion possible. The Church makes visible to the world the unity of those who follow Christ, and at the same time she makes that unity real—in fact, she is that unity. For this reason, the Second Vatican Council called the Church “the universal sacrament of salvation” (Lumen Gentium 48).

Belonging to the Church is not an optional extra for a follower of Jesus. It is an essential part of what it means to be His disciple and have a relationship with Him. As we have learned, Jesus founded the Church and made her the sign and instrument of humanity’s salvation. This truth means that through the Church, God leads humanity to Heaven. The Church is His instrument, or the means by which He accomplishes this mission of salvation. Through her, we receive the Sacred Scriptures. Through her, we receive Sacred Tradition, handed on from the Apostles. And through her, we receive the Sacraments, through which God’s grace flows to humanity. These Sacraments, especially Baptism and the Eucharist, are how God desires to dispense His salvific grace.