Pope John Paul II's address to the "representatives of the nations of the earth" at the United Nations today was his most important speech since becoming spiritual leader of the world's 700 million Roman Catholics.

It was far more than simply the appeal of a major religious leader for the end of war. John Paul issued a summons to "all the men and women living on this planet" -- as well as their political leaders and representatives -- to alter their material and economic values for the good of humanity.

The speech boldly placed him in the temporal arena of the way mankind organizes itself politically, distributes its goods economically, and establishes a moral and ethical purpose of life.

In range and context these were extraordinary things for a religious leader to address, and it was evident watching John Paul that he was deeply affected by his moment before the world's forum. Before he spoke in the huge General Assembly Hall, he sat in a chair several steps away from the podium, his chest heaving visibly as he waited to be introduced. After he completed his more than hour-long address, he sat again in that chair, his head bowed, appearing deep in contemplation and looking unusually subdued.

It was a humanistic message the pope delivered, predicated on the belief, as he said, that "all political activity, whether naional or international . . . comes from man, is exercised by man, and is for man." He drew the lesson and his main theme from that point by saying:

"And if political activity is cut off from this fundamental relationship and finality, if it becomes in a way its own end, it loses much of its reason to exist. Even more, it can also give rise to a specific alienation; it can become extraneous to man; it can come to contradict humanity itself.In reality, what justifies the existence of any political activity is service to man . . . "

This bid for leadership in world affairs represents something new for John Paul. In his previous foreign trips to Poland and Mexico and in last weekend's journey to Ireland, he stirred great emotion everywhere he went -- but he was speaking basically to the Catholic faithful.

Today he was attempting to reach people of all faiths and creeds, and those with none. And he was speaking not now just in the name of Catholic theology, but in the cause of humanity.

It was a speech noble in spirit and complicated in thought. In the end, of course, it probably left as many questions as it raised. But the principal question was to what extent the world's politicians, and its people, will heed the words of a pope interposing moral values on existing political and economic conditions.

John Paul already has amply demonstrated his moral concerns during this first year of his papacy. On his latest trips to Ireland and now the United States, he has repeatedly raised admonitions about declining moreal values and changing personal attitudes in a world increasingly secular. But, again, he was addressing principally Catholics.

In Monday night's remarks at the youth communion on the Boston Common, he restated much of what he had said to the Catholic youth of Ireland. "Do I then make a mistake when I tell you, Catholic youth, that it is part of your task in the world and the church to reveal the true meaning of life where hatred, neglect, or selfishness threaten to take over the world?" he asked. "Faced with problems and disappointments, many people will try to escape from their responsibility: escape in selfishness, escape in sexual pleasure, escape in drugs, escape in violence, escape in indifference and cynical attitudes."

Today he broadened that message considerably.

He looked back on the last century of great progress and of great wars, of striving for human rights and peace, and of continuing injustice and violence. He spoke of the outbreak of World War II, which began 40 years ago last month in his native Poland, and of "the whole of the experiences by individuals and nations that were sustained by a generation that is largely still alive."

Twice, he referred to the horrors of such German concentration camps as Auschwitz, in southeast Poland in the region where he was born.

"I would be untrue to the history of this century," he said, "I would be dishonest with regard to the great cause of man, which we all wish to serve, if I should keep silent, I who come from the country on whose living body Auschwitz was at one time constructed."

His point was that only by discovering what he called "the very roots of hatred, destructiveness and contempt -- the roots of everything that produces the temptation to war" -- can a more peaceful, equitable world society be established. That means such things as reducing economic tensions, ensuring the widest range of human rights and freedoms, and removing the "frightful disparities between excessively rich individuals and groups of the one hand and on the other hand the majority made up of the poor or indeed of the destitute."

As this is written, four hours have passed since the pope's speech. Outside the 17th-story window where I write, looking down on Fifth Avenue, confetti is pouring on the pope's motorcade below, the streets are thick with people, the balconies and windows are filled with citizens, cheers are rising in the city, and the bells of peace are pealing.

John Paul has their hearts today. Whether his words will change their minds tomorrow remains something else.