CREEDS ARE LIKE SEATBELTS. They won't do you any good unless you use them. The recent folly of the Episcopal Church, USA (ECUSA) shows what happens when a group says a creed but doesn't hold itself accountable to it.

Think of Luke Timothy Johnson's The Creed as a user's manual. It is not just an excellent commentary on the content of the Nicene Creed (more properly known as the Nicene-Constantinopolitan Creed). It is a handbook to faith, and its fundamental argument is that while faith is our very personal response to God, our response must be shaped by specific beliefs about God.

Johnson is a Roman Catholic New Testament scholar, and Protestants might not expect to hear a Catholic argue that faith is fundamentally a personal response to God. But Johnson, who teaches at Emory University's Candler School of Theology, was part of the wave of Catholic thinkers that, in the wake of Vatican II, rejected the church's old emphasis on faith as merely giving assent to propositions. They revived the personal and the communal, while de-emphasizing the priestly and institutional dimensions of faith.

Johnson still holds "as strongly as ever that faith in God is an existential response of the whole person characterized by trust, obedience, and loyalty." But over the past 30 years, he has seen where an emphasis on existential response—stripped of defining content—can lead. So now, he says, he has "come to appreciate how critical the role of belief is in structuring that response." Amen.

There is a popular tendency to dismiss the creeds as post-apostolic inventions that are, as Johnson writes, "instruments of politics rather than piety, of coercion rather than freedom, of philosophy more than gospel." Johnson straightens out ...