For the late John Paul II, the issue was Eastern Europe. For the new Pope Benedict XVI, the issue is Western Europe. History may find it difficult to judge who had the more difficult task.

I visited Poland in the early 1980s, not long after John Paul II had lit the spark that marked the beginning of the end of communism. It was clear, in Warsaw and other major cities, that Poland’s strong Catholic tradition had become a major rallying point in the battle for freedom. Inside, the churches were packed; outside, fields of votive candles burned brightly in testimony to the desire for freedom.

Over the years, I have much more often visited Western Europe, where the churches are virtually empty – only 20% of Europeans say religion plays “an important role” in their lives, compared to 60% of Americans, according to one poll – and the cathedrals serve as little more tourist sites.

Shortly before his election as pope, then-Cardinal Joseph Ratzinger identified the problem as a “dictatorship of relativism which does not recognize anything as definitive and has as its highest value one’s own ego and one’s own desires.” While his election reflected loyalty to the legacy of John Paul II, it also underlined the Roman Catholic Church’s recognition that its first order of business is to shore up its base at the historic center of Christianity.

Much of the secular press immediately jumped on the choice of Cardinal Ratzinger. The word most used to describe the new Pope has been “unbending” – as if a priest shouldn’t hold strong views about morality. Or, as Times of London columnist Gerard Baker noted acidly last week, the mainstream media headline might have read: “Cardinals Elect Catholic Pope. World in Shock.”

Well, perhaps the Catholic Church should be willing to bend on certain questions. That’s up to Catholics to decide. But it’s not as if this pope is an American Republican. He has been harshly critical of the Iraq war, for example, and like John Paul II he has often spoken out against the materialism implicit in capitalism. Nor has he been blind to the dangers of religious fanaticism.

Last year, he warned “If God’s image becomes something partial to the point of identifying the absolute of God with a concrete community or with certain of its interests, it destroys law and morality.”

But the new pope is clearly on to something when he worries that the pendulum in the West – and not just in Western Europe – may have swung too far in the direction of moral relativism and its offshoots. On university campuses, those who disagree with the multicultural agenda can find themselves marginalized, or even banished. In the press, religious faith is often treated as little more than a prejudice. No reference to God or even a Creator appears in the proposed European Union constitution.

When you drive out the priest, though, what you get is the witch doctor. Both John Paul II and Benedict XVI had close encounters with the great witch doctors of the 20th century, Stalin and Hitler. Ultimately both were overcome, but only at horrendous cost. Would a Europe – or a United States – bereft of faith find the moral courage today to make similar sacrifices?

Battling the dictatorship of relativism won’t be an easy task, particularly for a 78-year-old pontiff in a church which, as then-Cardinal Ratzinger admitted, has a good deal of “filth” in its own ranks. Among other things, Catholicism may be paying a price for having been the officially established church in many European countries. Thinking it had a monopoly on religion, it grew fat, careless and corrupt, leading to a severe reaction against all religion – unlike in the United States, where religion has mostly been a private matter and intense competition among churches is the rule.

But in taking the name of the patron saint of Europe, Benedict, the new pope signaled clearly that he intends to try to re-moralize the old Christian heartland. And Americans who believe that their rights come from Nature and Nature’s God, as the Declaration of Independence carefully puts it, have a big stake in the outcome.

Mr. Bray is a Detroit News columnist.