WE NO LONGER need to ponder what they can do to us. They have kidnapped and murdered our people. They have blown up our embassy. In 1980, the Ayatollah Khomeini did as much as anybody to determine the outcome of our presidential election and the course of our history.

Now they are doing it to us again. We are, as before, drawn up before television, devouring every word about negotiations, machinations, deals. We go into the homes of the returned hostages, we follow them to church, we speak with their mothers, fathers, wives, brothers and in-laws.

The details, in living color, absorb us. We watch bulletins, specials. Nothing is even vaguely comparable in fascination. What could approach the dramatic footage of the TWA pilot, smiling in the cockpit of the downed plane, despite the pistol held to his head, while the hand of the gunman slowly moves around to cover his mouth? That's what television by satellite does.

But maybe instead of this slavish attention to what is going on, we should be trying to find out what it is all about.

What do these people have against us?

Instead of watching the box to find out what they do, we might be better occupied reading about what they are thinking.

The point was made in a thoughtful article written by my colleague, Don Oberdorfer, for the Washington Journalism Review shortly after Hostage I was finally resolved. "Everyone concentrated on the screaming, fist-shaking mobs, but there was little exploration of who these people were or what they were screaming about. More difficult, but probably even more important, was reporting on the student culture out of which the hostage taking sprang. Hardly any journalists attempted it, in print or on the tube."

Four and a half years later, the same emphasis is on the pictures, not on the words. We know today as little about the hijacker's society, his motivation, his grievances and passions as we did the day the Iranians seized more than 50 Americans and locked them into our embassy. What in the world is a Shiite Moslem? What causes him to strap a grenade to his waist and drive a truck into a Marine compound, knowing he will be blown up in the explosion? Why are we to him and his maniacal fellows "the great Satan"?

The Shiites, it seems, are a Moslem faction which broke off from the main body of Islam in a bloody theological dispute centuries ago. They constitute barely a tenth of all Muslims, have been hounded and persecuted for centuries. According to a Polish writer named Ryszard Kapuscinski, "They live in memory of the centuries of pogroms against them, and so they close themselves off in ghettoes, use signals only they understand and devise conspiratorial forms of behavior."

Despised and downtrodden, they gathered in Iran. "They have been ruled for centuries on end by foreigners or local regimes dependent on foreign powers, and yet they have preserved their culture and their langauge, their impressive personality and so much spiritual fortitude, that in propitious circumstances they can arise reborn from the ashes."

The Ayatollah Khomeini is their leader. His revolution in Iran, which to Western eyes brought in a dark time of tyranny, backwardness and isolation, is a shining triumph to the Shiites, who hope to repeat it in Lebanon.

In an open letter to the Hezballah, the Party of God, the most extxreme Shiite faction, their leaders, the imans, outlined the political realities this way:

"We, the sons of Hezballah's nation, whose vanguard God has given victory in Iran . . . abide by the orders of a single wise and just command currently embodied in the Supreme Ayatollah Khomeini, the rightly-guided iman . . . who has detonated the Moslems' revolution and who is bringing about the glorious Islamic renaissance."

And, "America is behind all our catastrophes . . . . America and its allies in and the Zionist entity that has usurped the sacred Islamic land of Palestine . . . they have attacked our country, destroyed our villages, massacred our children . . . and installed over our heads criminal henchmen . . . . Their bombs fell on our kinsmen like rain during the Zionist invasion of our country and the Beirut blockade."

There is more like this, but it gives an idea of the fanaticism being played out in the anarchy of Lebanon, and reason to believe that the end of Hostage II may not be the end of terrorism.

There is of course a limit to understanding terrorists. You can read the history of Ireland and in a single chapter about Oliver Cromwell discover why hatred and bitterness have endured for so many centuries. But after a while, the why doesn't matter.

But perhaps we should at last inform ourselves somewhat about the inflaming certainties of Islam, which considers murder in the name of God a virtuous act and kidnapping of representatives of the "Great Satan" an admirable occupation.