In the Persian Gulf, the world is witnessing the disastrous result of unrestrained arms sales.

Iraq and many other countries have found it easy to build huge arsenals. For the United States, the Soviet Union and their allies, weapons are one of the most influential tools of foreign policy.The main rationale for selling weapons - especially in the Middle East - is to help an ally ward off threats from neighbors, to maintain the "balance of power." In other instances, governments attempt to trade guns for cooperation, even from hostile countries.

But diplomatic agendas are only part of the story. Weapons sales are also attractive on a strictly commercial level. Arms have become one of the principal exports for industrialized countries like the United States and Soviet Union and for developing countries like China and Brazil.

In truth, weapons sales rarely achieve anything but profits. Conflicts in the Middle East and elsewhere show that arms sales don't engender peace or stability.

Using weapons as a tool of diplomacy is a chancy business. Sales certainly don't beget loyalty, as shown by Egypt's defection from the Soviet camp in the 1970s.

It is hard to predict and impossible to control the outcome of weapons deals. That was one of the lessons of the Reagan administration's attempt to win Iran's help to free American hostages from Lebanon.

The economic benefits of the weapons trade are also dubious. Sellers may profit, but Third World countries facing intractable economic problems are handicapped further with huge outlays for arms.

In the wake of the Persian Gulf conflict there will be more pressure than ever for arms sales in the Mideast and elsewhere. We must learn the real lesson of this commerce and this war. Unless the flow of weapons is cut off, the hope of a changed world will never be fulfilled.