IF THERE IS ANYTHING USEFUL to be learned from the Iranian situation, it is that we as a government and we as a people know precious little about the internal politics and national psyches of most Third World countries. We don't understand their religions, their revolutions, their logic, their hatred of imperialism, their power blocs and their obsessively clandestine politics.

Shortly after the hostage seizure, I talked to a well-educated Iranian professional man who has lived in the United States for years. He knows how we think, and he knows how the Iranians think. He predicted that there would be no breakthrough in the hostage stalemate until the American news media were out of Iran and the factions in that country could begin subtle, secret maneuverings toward change. No political or religious leader, he said, could risk losing face or power by coming forward first on behalf of releasing the hostages.

He was right. It was only after the American news media were expelled that there was any sign of movement, however slight. He understood, in other words, the conspiratorial politics of the Iranian revolution that are so generally alien to the American political experience.

Usually, when we're having a presidential election year and the incumbent president makes a bold move such as Carter has done in severing ties with Iran, some other presidential candidate will dissect the move in a fashion that might enlighten the public. But the current candidates reacted to Carter's stroke with such a united front of wishy-washy rhetoric that I was left, to put it nicely, bereft of guidance. Would this do any good, or had Carter managed to lose hold of the situation, much the way parents do when they throw up their hands and kick a teen-ager out of the house.

I called our Iranian acquaintance, who has just returned from visiting his family in Tehran. That is why he does not want his name in the newspaper. He thinks Carter made the right move, but he does not think it's enough. "If he is going to get tough, he has to go all the way. I don't know if the United States is ready for that.

"Khomeini has a very narrow scope of mind. He is not going by logic. He is going by what he senses. He senses that if he gives up the hostages, then they're not going to let him stay in power and he loses his position. Suppose the hostages come out of Iran? Then nobody needs Khomeini. There are other mullahs who are smarter than him. They will take over. He is afraid of losing power. He is not going to give up until he is forced to do it. That takes either a civil war inside the country or takes military action on the part of the United States . . . [that will] create such chaos that people will start thinking of doing something themselves."

"I hope they won't throw the students out of the United States. They are the only hope of resistance against Khomeini," he said. "The students you see in the streets, they are not the whole 65,000 [Iranian] students we have in the United States. There are a lot who are not for what is going on in Iran."

He says the United States should continue to offer asylum to Iranians trying to flee the revolution, instead of revoking visas of Iranians not in the United States. And he cautioned that some of the Iranian military and quasi-military personnel who are being expelled from the United States face uncertain and perhaps dangerous futures in Iran.

"I've just had calls from people who are in the military wanting to know what's going on now that they are forced to go and maybe face trial. There are students who were sent by the shah from different branches of the armed forces. They were not planning to go back because obviously the regime is not for them now. . . . They don't know what to do." The expulsions of military personnel, he said, "should not have been done in a blanket way."

He drew grim pictures of a disintegrating society run by neighborhood communities. "It resembles what the Mafia had in the '30s in different parts of New York." He said nurses in hospitals don't listen to the doctors, and there is no authority in government agencies and factories. "The workers just get together and throw out the manager and they sit down and don't know how to run the factory."

While the country is nearing chaos, Khomeini is hanging on for dear life by carefully balancing rival blocs against each other. "The power play is now mainly between [President Abol Hassan] Bani-Sadr and [Ayatollah Mohammed] Beheshti," who is secretary general of the Revolutionary Council and its presiding officer. "He is trying to push Bani-Sadr out and he has been succeeding.

"When I was inside Iran, I was told that Beheshti has the backing of maybe the British and the Germans.The British, out in the open, are with the United States, but they may play a role in pushing us out and taking over. These are all speculations, but they sound reasonable. In 1953, when Mohammed Mossadegh was in power, the United States did this to the English. The oil was British. The whole situation turned out to be that the big cartels from the United States wanted a share. Now the situation is reversed. The English may be feeling confident enough to push the United States out.

"If Beheshti is listening to the British, then they may have leverage because Beheshti is becoming more and more powerful there. The mistake Bani-Sadr made is he started doing something that was against Khomeini's power so Khomeini started feeling a little bit threatened. To equalize power and to keep himself on top, Khomeini brought up Beheshti and the religious groups. Now he is playing with these different groups just to keep himself on top.

"Beheshti is a smart man. I think if he knows he is going to get something out of it, he might work out a deal through the English and the United States."

But if the United States finds it has no leverage through its allies to get the hostages out, it can either go in militarily, soon, or "simply forget about those people and sit and wait and do nothing. Just threats, without any power behind it, is the worse thing they can do. To have threats like this means nothing. The only thing it does is incite the people.

"Carter has to follow through. My prediction is pretty soon he will have to go further and further and the only thing will be military action."