According to the Heidelberg Catechism, to affirm “one holy catholic church” means, “I believe that the Son of God, through his Spirit and Word, out of the entire human race, from the beginning of the world to its end, gathers, protects, and preserves for himself a community chosen for eternal life and united in true faith. And of this community I am and always will be a living member.”

 - The Christian Faith: A Systematic Theology for Pilgrims on the Way (Horton, Michael S.)