The Athanasian Creed, written around the Sixth Century, was named for Athanasius, a delegate at the Fourth Century Council of Nicea. That was an "ecumenical" church council, meaning it included representatives of Christianity from all around the world. The creed named for Athanasius expresses the biblical doctrine that he believed, taught, and confessed. His name was chosen because of his prominence as a defender of biblical Christianity against the sects of his day that had chosen another way.
The Athanasian Creed, as quoted in our Evangelical Lutheran Hymnary (p. 29), begins with this statement:
Lutherans use the Athanasian Creed as our own confession of faith. We confess the words in the previous paragraph. It may surprise some people, because that statement requires us to hold the "catholic" faith, rather than the "Lutheran" faith. Yet that surprise betrays a misunderstanding of the word "catholic."
The word "catholic" was reportedly first used by Irenaeus, whose death we commemorate today, as these words are being written. It refers to the things shared by all Christians, regardless of where they live, what nationality, race, or customs they may represent. In the Athanasian Creed, "the catholic faith" is the doctrine that all genuine Christians believe, teach, and confess.
The word "catholic" is just as much an inclusive word as an exclusive word. That is, it includes many different kinds of people as readily as it excludes the others. A point of disagreement between Lutherans and many others in our time is what criteria determine whether something may be considered "catholic." Lutherans believe that the criteria are summarized in the Athanasian Creed, as well as the Apostles' and Nicene Creeds. We regard the word "catholic" as a description of what we believe, teach and confess as true, rather than a description of our loyalty to any earthly institution.
Lutherans use the word "catholic" as an adjective. Followers of the Pope use the word as a label or title, the same way the word "Lutheran" is used as a label. Just as some Lutherans no longer agree with the teaching of Martin Luther, so also some who call themselves "Catholic" no longer agree with the catholic faith as summarized in the ecumenical creeds. Yet when used as an adjective, "catholic" is a fitting and accurate description of what the Confessional Lutheran Church teaches. Therefore, the character of confessional Lutheranism is rightly described as "catholic." We hold to the catholic faith, whole and undefiled.