Pope John Paul II's emotional homecoming has demonstrated at least two things, one positive and one negative.

He has, first of all, provided a striking answer to Stalin's sneering question about the powerlessness of the papacy in the modern world: "How many divisions does the pope have?" As many as are needed, John Paul's journey seems to say.

What Moscow cannot fail to note, and what people throughout the world have witnessed through telecasts, is that this Polish pope carries the power to muster millions. Day after day, the scenes of vast Polish crowds stretching as far as the eye could see were awesome.

By his presence and his words, the pope rallied his fellow Poles, lifted their spirits and summoned their support in a ceaseless struggle against totalitarianism. His message bordered on the audacious. On virtually every public occasion, he boldly challenged the state on the most fundamental questions of freedom.

That he is a force to reckon with hardly needs to be stated. It is difficult to recall a time when a public figure has so moved an entire nation in ways that hold such potentially fateful consequences.

And that is part of the problem.

It is said that when Woodrow Wilson went to France at the end of World War I, everywhere expressing his dream of a League of Nations that would banish war from the Earth, the millions who turned out to cheer him did so with an emotional fervor that was frightening in its intensity and spontaneity. Reporters who accompanied him wondered whether even a Caesar or Napoleon had ever stirred such an emotional outpouring from the masses.

The aftermath, of course, was a disillusioning letdown, perhaps the inevitable reaction that sets in when the cheering stops. Instead of the dawning of an era of international peace and good will, a weary world yearning for stability and security saw only the unleashing of an arms race that led to even greater human slaughter and economic destruction. In the end, dreams of universal disarmament were dashed by the possession of the most fearsome weapons known in all of history.

For Poles, the end of the pope's pilgrimage to their common land is certain to result in some sort of letdown. It cannot be otherwise. Such emotion simply cannot be sustained in the face of harsh realities that will remain.

The question is whether the aftermath of his visit will lead to more repression or a reduction of tensions. Eastern European history in the post-World War II Soviet era is not encouraging.

Each time the impulse for freedom has arisen in strength it has been brutally crushed.

In Hungary, in 1956, it was freedom fighters courageously but vainly hurling bottles against Soviet tanks in their capital of Budapest, with the result preordained. In Czechoslovakia, in 1968, after the Dubcek reforms of the spring inspired dreams about the possibilities of "socialism with a human face," again it was Soviet tanks rumbling through the streets of Prague, snuffing out hopes for a new era.

No story I have covered produced such painful memories as those stemming from the collective sense of despair displayed by people after their dreams have been crushed. Now, like the Hungarians and the Czechs, the crucial time of testing for Poland seems to be approaching. It requires the greatest delicacy, statesmanship and, especially, calm. The last thing Poland needs now is more emotion. The challenge lies equally with church and state.

Through all the years of Communist domination of Poland, it has been the fervent, unyielding stance of the Roman Catholic Church more than anything else that has kept the Polish people united. Part of this springs from the nature of the Polish Catholic Church: it represents an older, more dogmatic, more clannish brand of Catholicism. And part comes from necessity: in Poland, the lines between church and state, Catholicism and communism, could not be more sharply drawn.

John Paul's trip has brought home forcefully to Polish authorities, and the Russians, one immutable fact. The hold of the church on the people has been strengthened even more.

If they didn't know it before, they cannot escape another fact. Threats of force and martial law notwithstanding, the Poles have demonstrated that resistance to repression cannot be bled out of them. Their desire for freedom will not be quenched.

The authorities, and again especially the Soviets, also know something else. While the church has the people, they have the tanks. And they have shown amply enough that they know how to use them with maximum force and effectiveness.

For both church and state, the trick now is not to let themselves be stampeded by emotion and fear into another tragic replay of Hungary and Czechoslovakia.

In that respect, what W. Averell Harriman said during a recent conversation with this reporter is worth considering. He was speaking in the context of Soviet-American relations, a subject he perhaps knows better from first-hand experience than anyone, but his points also apply to Poland and the Soviet Union now.

"I think we can come to an agreement with the Russians if we go about the negotiations in the proper way and not call each other names," Harriman said. "Unfortunately, starting with President Reagan, we've got ourselves in a very antagonistic attitude rather than a collaborative attitude. By that, I'm not in any way suggesting that we accept the Soviet system. That's their idea. There is nothing we can do to change it . . . .

"There is no use insulting them. You want to be firm. In negotiating with them you want to find the areas in which we agree. There are plenty of areas in which we disagree. Find those areas in which we agree, and try to make progress. We can either have a confrontation with them or some sort of conciliation."

The same reasoning applies to present conditions in Poland. Church and state have much to disagree about, but they also have a common interest in reducing destructive conflicts in their homeland. That, too, has been the pope's message. Now we will see whether the state understands the power of that appeal as well as the people so obviously do.