Amid the motorcades, million-plus crowds and rave press notices for his personal warmth, Pope John Paul II is likely to bring Americans one message: Serve God and love one another.

Every pope since the excitable St. Peter and every spiritual leader back to Moses on the mountain has said that.

But how specific will the pope dare to be? When he is in Iowa, will he have a few angry drive-them-from-the temple words for Catholics who own or manage the giant agribusiness firms that are ruthlessly driving small farmers off the land?In the South Bronx, what will he tell Catholic slumlords? In Boston and Chicago, will he wonder aloud why Catholic hospitals have reputations for being anti-labor and anti-union? In Washington, will he remind the Catholics in Congress about church teaching on abortion?

In Mexico and Poland, linguists skilled in de-coding Vaticanese were needed to penetrate the subtlety of John Paul's words. American Catholics are different. An appetite for directness and a taste for specifics is a mark of the church here. In the past few years, its leaders haven't held back in advising either their own members, or secular society as a whole, in ways that people should love each other.

Much of the message doesn't come from the pulpit at all, but from riskier platforms. Currently, the United States Catholic Conference has five full-time government relations staff people -- backed by 15 to 20 others -- who lobby Congress on nearly every major social issue. From cloakroom buttonholing to cardinals testifying before the Senate Foreign Relations Committee, Catholic social doctrine is applied to political debates on welfare payments, housing, national health insurance, the death penalty, poverty programs, abortion labor laws and military policy.

With the American church having developed a strongly activist style of religion, a large part of the pope's national audience will be watching to see how boldly he takes on the hard questions. A long line of encyclicals on justice and peace has come from Rome since "Rerum Novarum" of Pope Leo XIII in 1891. Not much more can be added to these aggressive statements.

In 1971, the policies were summarized by the synod of bishops' document "Justice to the World": "Action on behalf of justice and participation of the world fully appears to us as a constitutive dimension of the preaching of the Gospel, or, in other words, of the Church's mission for the redemption of the human race and its liberation from oppressive situation."

Those are stirring words. But when taken to the depths of a specific "oppressive situation" what can be stirred up is a sea of rancor.

A current case illustrates it. The Sisters of Loretto in central Appalachia are suing the Blue Diamond Coal Company, owned by prominent Catholics. The nuns, angry about the company's poor record on safety and environmental issues, are seeking to have corporate policy reflect a few of the church's teachings. How can you love God, they wonder, by despoiling the land? But the firm thinks the nuns are unholy nuisances who have broken with their vocation.

Actually, the sisters are doing little more than applying the generalities outlined in a recent pastoral letter from Appalachia's bishops on the victimization of coal miners and abuses to the land. For all too many Catholics, though, as well as outsiders, when the hierarchy speaks out on social issues it is esteemed as "church teaching." When someone applies the lessons to specific cases, it is hell-raising.

The church is lucky to have groups like the Sisters of Lorette, though it is the kind of luck that has to be paid for. Offend too many Catholic board chairmen and soon they'll be sending checks to the Urban League, not Catholic Charities.

What is lost in dollar, though, may be made up in devotion. A few years ago, John Cogley, the late journalist, described what began to happen in the 1960s and which continues until today. "The church we grew up in was almost totally clericalized. For most of the laity the church was something that belonged to 'them,' the clergy. When the church spoke, it was 'they' who were speaking. We simply did not think of the church as ourselves, or of ourselves as part of 'them.' Laymen had a place in the church, to be sure, but rather as associate members, pewfillers. . . Vatican II has changed that attitude -- or at least one hopes it has. Already, we laymen have been saying bravely if a little incredulously, 'We are the church.' But the fortunes of the church of the future in this regard depend on all of us. We still have to get used to the idea that we take the church with us everywhere we go. We can no more escape this responsibility than the church can cease to acknowledge our presence in it."

If so many laymen, as well as groups like the Loretto sisters, are taking risks in applying their beliefs to the daily events, that is what many are wondering on the eve of the pope's visit:

How offensive and how specific is he willing to be in stating the church's objectives and calling attention to its values? St. Teresa, the Spainard and one of history's authentic feminists, offered some guidance: "We cannot know whether we love God, although there may be strong reasons for thinking so, but there can be no doubt about whether we love our neighbor or not."

If, after a week in America, a few of those doubts are removed, John Paul's visit will have been worth his and our time.