In his kindly way, Pope John Paul II brings a most stern message to America. Everywhere he goes, he warns against materialism, against selfishness, and the failure of nations and men to help those he calls "the poor and the powerless." He's been calling for "reforms, even profound ones, of attitude and structures," and has both rebuked and challenged affluent America and its way of life.

"The poor of the United States and of the world are your brothers and sisters in Christ," he says. "You must never be content to leave them just the crumbs from the feast. You must take of your substance, and not just of your abundance, in order to help them. And you must treat them like guests at your family table."

These words do not come late to this pope. Since his elevation to the papacy a year ago this month, he's spoken often of the unjust divisions between the rich and the poor, whether nations or individual men and women. "Christians will want to be in the vanguard in favoring ways of life that decisively break with a frenzy of consumerism, exhausting and joyless," he said early in his reign.

But he has given that message greater emphasis on this American tour. Indeed, the theme runs virtually through all his appearances.

When he speaks critically of "rich and permissive" societies, there's no doubt that he's speaking of America, the center of the capitalist world and the heart of the consumer society.

"It is not right that the standard of living of the rich countries should seek to maintain itself by draining off a great part of the reserves of energy and raw materials that are meant to serve the whole of humanity," he says.

That's unsparing language -- and it represents a clear challenge to the existing order.

To this reporter, the strongest, most moving expression of the pope's views came during last night's mass at New York's Yankee Stadium. Toward the close of a splendid evening marked by eloquence and ceremony, the pope, speaking in the slow, deliberate style that conveys an unusual sense of power, recalled the biblical parable of the rich man and Lazarus.

"Once there was a rich man who dressed in purple and linen and feasted splendidly every day," he said. "At his gate lay a beggar named Lazarus who was covered with sores. Lazarus longed to eat the scraps that fell from the rich man's table."

He went on to say that the rich man and the beggar died and were carried before Abraham, and judgement was rendered. "And the scripture tells us that Lazarus found consolation but the rich man found torment." The pope drew this simple lesson: the rich man earned condemnation because he turned away from someone who sat at his door and longed for the scraps from his table.

"Nowhere does Christ condemn the mere possession of earthly goods as such," the pope said. "Instead, he pronounces very harsh words against those who use their possessions in a selfish way, without paying attention to the needs of others."

Earlier in the day, John Paul challenged all nations to take a more humanistic approach in their dealings with one another. By nightfall, he had become more specific: The rich countries -- and now by clear implication, the United States -- must take the lead to "translate into contemporary terms, in terms of economy and politics, in terms of all human rights," actions that would alleviate poverty wherever it was to be found.

At every stop on his American tour, the pope has emphasized the plight of the poor and urged that greater steps be taken to help them. Standing in front of St. Patrick's Cathedral before leaving on his motorcade to the blighted areas of the South Bronx and Harlem, he said: "In a special way my heart is with the poor, with those who suffer, with those who are alone and abandoned in the midst of this teeming metropolis." Later, still in Harlem, and speaking directly to blacks, he spoke of people who "feed on emptiness and tread the path of despair."

You didn't have to look far to find them, he said, for "they live in our neighborhood, they walk down our streets, they may even be members of our own families."

There was no let-up today. What he had to say late this afternoon in Philadelphia seemed to have a special application in a city stained by civil disorders, ugly divisions of race, and charges of police brutality during the administration of Mayor Frank Rizzo. The people of Philadelphia, he said, must strive to preserve the human values of equality and freedom expressed in the Declaration of Independence and "understand them better and . . . define their consequences for the whole community."

He asked them to "assume more fully your duties and obligations toward your fellow human beings." He spoke of reform, of ending the exploitation of man by man, of promoting "upright service and honesty in public servants."

He spoke softly, but again there was no mistaking his intent.