One supreme theme of Christmas returns this year to its place of origin. The prospect of peace on earth shines forth in Bethlehem and Jerusalem and Galflee and other spots, sacred and profane, in the Mideast.

But not thanks to another Christmas theme - goodwill toward men. On the contrary, today's effective peacemakers are mainly driven by vanity, chauvinism and massive political self-interest.

The decent, disinterested approach to an accord between Arabs and Israelis finds its most notable exemplar in the Carter administration. The President and his advisers sought peace and goodwill based on fair treatment for all parties. The claims of Israel and Egypt, of Syria and the Palestinians would all receive a hearing in a comprehensive settlement to be arranged at Geneva under the even-handed supervision of the U.S. and Russia.

That emphasis did not yield nothing Mr. Carter's ceaseless stress on the rhetoric of peace made it hard for anybody to take a hard, bellicose line. But creating a favorable atmosphere is all the administration can justly claim as a positive outcome of its drive for a Geneva settlement.

It happened, however, that the right atmosphere had an unintended impact on the two principal peacemakers. President Anwar Sadat needs a settlement in part because Egypt's economy is, as he told me and many others recently, "horrible." Only by stopping the drain of trained men and other resources for the military can he arrest the progressive deterioration - the Indianization - of his country.

In addition, the President and, even more, his army and people are, as he told me, "fed up" with bleeding and dying for other Arab causes. They do not like deferring one bit to Syria or the Palestinians or Libya or Algeria or even Saudi Arabia. They feel, as Sadat put it, that "Egypt is the greatest Arab state . . . and the most ancient and most capable."

But in the runup to the Geneva conference envisaged by Washington, Sadat found himself playing second fiddle to Arabs less interested in a settlement than in pressing demands on Israel - notably the Syrians and Palestinians. After the joint American-Soviet call for Geneva, he came to believe that, as he told me, Geneva would yield not settlement but an endless process of "semantic discussion." To break out of that bind, to assert Egypt's freedom of action against the other Arabs, he retreated forward. He went to Jerusalem.

Now he is almost totally committed. His authority in his own government, particularly with the military, his standing with the Egyptian people, his status among other Arabs, and his prestige in the world all depend on making good the peace initiative he took on the trip to Jerusalem. He cannot afford to fail.

Similarly with Prime Minister Menahem Begin of Israel. The prospect of a Geneva conference shaped up as a nearly total disaster for him. He foresaw the United States, Russia and all the Arabs forcing Israel to treat with its mortal enemy, the Palestine Liberation Organization, on an agenda that included the possibility of an independent Palestinian state on the West Bank of the Jordan River.

Sadat's trip to Jerusalem averted that dreaded danger. It opened the opportunity of working out a settlement with Egypt and the moderate Arabs in Jordan and on the West Bank free from the insistent pressures of the Russians, the Syrians and the radical elements of the PLO.

To be sure, Begin will have to make concessions on the West Bank that he once refused even to consider. But he is being pushed in that direction by his most prestigious advisers - Foreign Minister Moshe Dayan, Defense Minister Ezer Weizman and Deputy Premier Yigal Yadin.

He has more at stake even than Sadat. His whole history as a Jew and a Zionist is on the line. If by a lack of imagination or an excess of rigidity he misses this chance for peace, he has nowhere to go in the Mideast. He is finished in politics and in life.

Begin and Sadat, in other words, are peacemakers out of desperation - not goodwill. Their motives are not as high-minded, nor their instincts as generous, as those of the President and his men. But by a not unfamiliar paradox, peace on earth has a better chance if the men of goodwill leave the leading roles to less figures who cannot afford to fail.