To those for whom religious "preference" is of no more consequence than any other lifestyle choice -- something like Saab or Volvo, Nationals or Orioles, medium-rare or rare, chardonnay or chablis -- the recent document from the Vatican's Congregation for the Doctrine of the Faith, clarifying once again the self-understanding of the Catholic Church vis-a-vis other Christian communities as that self-understanding was expressed at the Second Vatican Council, can only sound strange, even offensive. To those who take seriously Christ's promise that he would preserve his Church in truth through the power of the Holy Spirit, the CDF clarification (approved by Pope Benedict XVI) is an invitation to serious theological conversation. That conversation emphatically includes theologically serious Christian believers in non-Catholic Christian communities. So let's try a little theology.

There is one Church of Christ for, as St. Paul taught, the Church is the body of Christ and Christ has but one body. The unity of the one Church of Christ fractured (formally) along an east-west fault-line in 1054. The unity of western Christianity fractured in the 16th century and has been re-fracturing ever since (witness the latest sorrows of the Anglican Communion, or the northern Baptist/southern Baptist split during the American Civil War, or any of hundreds of other examples). But whatever the fractures, and along whatever fault-lines, all those who are baptized in the name of the Trinity are baptized into the one body of Christ. So all the baptized are in a real but imperfect state of communion with each other.

Why "imperfect?" Because different Christian communities have different understandings of the nature of the Church that is the one body of Christ. To ignore these differences as if differences make no difference is to say that the truth of the Church which Christ bequeathed to the Church makes no difference. So genuine ecumenism means engaging differences with respect and civility, not ignoring differences. Rodney King was no theologian, and "Why can't we all just get along?" is not a maxim for serious theological dialogue.

The Catholic Church, at the "liberalizing Second Vatican Council" (to use the standard journalistic trope), declared that, according to its self-understanding, it is the fullest, most rightly-ordered expression of the will of Christ for his church. The Catholic Church also acknowledged, at Vatican II, that there are important and life-giving elements of sanctification and grace in other Christian communities. So the question became, how say both of these things at once: how say that the Catholic Church is the most rightly-ordered expression of Christ's will for his Church and that the grace of Christ works through Christian communities that have a deficient concept of Church order from the point of view of Catholic doctrine?

The Council fathers decided to use the Latin phrase subsistit in -- the one Church of Christ "subsists in" the Catholic Church -- in place of the Counter-Reformation formula, according to which the one, true Church of Christ "is" the Catholic Church, for that formula seemed to preclude the possibility of grace operating through other Christian communities. An ocean of ink has been spilled over the nuances of subsistit in since Vatican II, but the essential points remain: the Catholic Church believes itself to be the most rightly-ordered expression of the will of Christ for his Church and the Catholic Church believes that the grace of Christ, in the Holy Spirit, works in and through other Christian communities. (Which of these communities are "Churches" and which are "ecclesial communities," as the Catholic Church understands them, has to do with the sacramental system, or lack thereof, in these various expressions of Christian faith.)

The Catholic Church cannot, will not, and, frankly, should not suggest that it is but one consumer option in a supermarket of Christian possibilities. To do so would be to reduce ecumenical dialogue to a vague exchange of pleasantries, of no real consequence because the exchange really has nothing to do with the truth -- the truth that Christ promised to the Church. That the self-understanding of the Catholic Church creates tensions with other Christian communities is obvious; those are, however, creative tensions, as they lead to genuine exchanges of insight. That is the lesson of the most developed ecumenical dialogues of the past forty years -- between Catholics and Anglicans, Catholics and Lutherans, Catholics and evangelicals -- and, because of the nature of the Church and the nature of religious truth, that's the way it's going to be in the future.

One part of the one Church of Christ has achieved full unity, as the late Pope John Paul II taught -- and that is the Church of martyrs. Having given their lives for Christ, and thus having borne the fullness of witness to the truth of Christ, the martyrs now live in the fullness of unity with Christ that continues to elude the Church in history. The 20th century was the greatest century of martyrdom in Christian history, more Christians having been killed for their fidelity to Christ in the last century than in the previous nineteen together. Those martyrs were Anglicans, Orthodox, Protestant, and Catholic. Their unity in Christ ought to be a spur to an intensified quest for unity-in-truth in the body of Christ here and now.