At Christmas time the phrase trips trippingly off the tongue. Its two parts hang together like terms of a self-evident equation. But does good will toward men equal peace on earth? Well, not judging by the present conjuncture of world politics.

No American president of the postwar era surpasses Jimmy Carter in benign feelings toward the rest of mankind. He cares about the starving masses and can fairly claim to have heightened American concern for the porrer countries of the southern continents -- the so-called Third World. He sets great store on righting wrongs done by Americans to other groups and countries in the past. He speaks of warm personal relations with other leaders, as though friendship were the ruling principle of foreign policy. But with what results?

President Lopez Portillo of Mexico presents the case of a leader whom Carter leaned over backward to please. In Mexico City, Carter joked when Lopez Portillo dressed down the United States. In Washington, Carter praised as "the most profound and beautiful I have ever heard" a speech by Lopez Portillo to the United Nations that was so commonplace it found no notice in the American press.

By way of repayment, Carter has received kicks and shoves. Mexico has been among the leaders in forcing up the price of oil. Apart from taking cheap shots against this country on the dollar, Lopez Portillo has twice broken commitments to the United States -- once in the course of the natural gas negotiations and a second time with respect to receiving the shah of Iran after his surgery in New York.

Vietnam and Cuba provide examples of efforts by the Carter administration to make up for what it deemed to be the immoral actions of the past. In each case, the administration moved, as a gesture of good will, to resume diplomatic relations.

But Hanoi continues aggressive action against its neighbors. The war waged by the Vietnamese has already brought mass starvation to Cambodia. It threatens to drag in China, and Russia, and maybe even the United States.

Fidel Castro, far from relenting in hostility toward this country, expands the area of confrontation. Cuban expeditionary forces make proxy war on behalf of Soviet interests in southern Africa and around the Persian Gulf. Havana seeks to cast the economic demands of the Third World in the shape of a challenge direct to Washington.

Last, there is the tragic case of Iran and Ayatollah Khomeini. President Carter did not lift a finger to save the shah. Those of us who saw Carter at the time remember vividly his talk of the Iranian constitution of 1906 and the role of the Majlis, or parliament. He spoke of the ayatollah as a religious figure, not interested in politics.

Once the Khomeini regime had asserted itself, the United States went out of its way to court friendly relations. This country sent heating oil and arms to Iran, even though the Iranian government occupied American installations in that country and refused U.S. Officials access to their own records. It was in those circumstances that the Iranian seized the American Embassy and took the hostages.

That action now undermines American interests and positions all around the world. As the recent shoot-out in Mecca demonstrates, the Islamic fundamentalism distilled in Tehran threatens Saudi Arabia and the other friendly monarchical regimes up and down the Persian Gulf. They respond by taking their distance from the United States. They raised their oil prices by a third at the OPEC meeting in Caracas last week, and will probably raise them again later this year. Their production schedules are now reined in to the point where OPEC oil output, which was due to expand until about 1985, has probably reached its peak now.

At the same time, the turbulence of the ayatollah's regime shows up all around the edges of Iran. It makes for instability in Afghanistan, Iraq, Pakistan and Turkey, and in those countries there is now opening up a new theater of engagement between Russia and the United States.

Americans, to be sure, are not dying in foreign combat this Christmas. There is virtually no prospect of a nuclear war between Russia and the United States. Still less are the chances of an over-the-top attack in Europe.

But in those areas, the Carter administration has followed traditional policy. The new departure has been the turning of the other cheek in the Third World. In that quarter, troubles abound and there sound "ancestral voices prophesying war." So at the least, experience fosters second thoughts as to whether peace can come purely from good will, as a kind of present from Santa.