IT'S NOT JUST the president who has to make choices. The taxpaying, consuming American public, the American political apparatus, and that many-parted structure of private interest groups that represents everything from athletics to farming to industry have been forced into a position of choosing. They have been so forced by the Russian actions in Central Asia and around the Persian Gulf. This is the case as well for comparable individuals and groups in Western Europe and elsewhere in the world.

Choice is the key word. One of the principal follies of American political thought in recent years has been the crazy unexamined premise that any sanction we might impose on others by way of punishment or pressure or reprisal or even self-defense needed to be "free" -- free in the sense of that proverbial "free lunch" we are always admonished doesn't exist. But free sanctions don't exist either. They necessarily cost us something. That is what the choice is about.

Merely articulated, this much may seem self-evident. But a failure to grasp the elementary truth of it has confounded the reasoning of many of those most passionately engaged in the foreign policy deliberations and debate of recent years. The theory has been that if any step we might take against the Russians had some adverse effect on us or a perceptible cost, it was fatally flawed.

Thus we have resisted using trade, agricultural sales, arms control deals, sports and cultural back-and-forth or just about anything else you can mention, including most prominently any show of force at all; any of this would either hurt some among us or inconvenience them dreadfully or lose us friends eslewhere or result in its own reprisals or something. And having been unwilling to sift among these various alternative risks and costs, we have sunk toward a kind of international political paralysis. We much prefer to define the problems away or lapse into that pretentious and self-deluding psychoanalysis of our antagonists which immediately can discover some pitiful reason of weakness and fright on their part, fueled by misconduct on ours, that has caused them to behave in so beastly a way.

Now President Carter, impelled by a rapid progression of truly ugly events, has broken out of that frame of mind, been forced out of it really. He is not deciding whether to respond but rather what to do. The course he is on will first require that a wide array of constituencies and leaders around the country be willing to make some choices themselves. Are the wheat farmers really going to prevail in the discussion of curtailing agricultural exports to Russia? Are the people who have some private stake in the Moscow Olympics really going to help Moscow in its exercise of self-legitimization by insisting that the games go on in the name of the grand-sounding but transparently absurd proposition that all sports are above all politics? The U.S. and the Western Europeans and any others who care to join simply should not participate in the Moscow games.

Other realms of action are delicate but no less promising and important. We think the president's statement on SALT, "deferring" it until the crisis brought on by Soviet aggression has been dealt with -- a cold and correct statement -- was just right. Even though Senate approval had become doubtful, had the president tromped all over the accord and chucked it out as a bad and perilous deal given the fresh Russian treachery, it would have meant the absolute end of agreements that may conceivably be useful in the future -- useful to both us and the Soviet Union. But he has, at last and properly, conceded that there is some point where linkage, that much maligned concept, is wholly valid.

A second delicate but important area of prospective action concerns Defense Secretary Harold Brown's trip to China; he leaves today. This has been a politically consequential journey from its inception.It becomes more so now. Surely in view of the Afghan adventure and the cynicism and the lying that accompanied it, the Brown mission should be allowed a good deal more leeway in making defense arrangements with and for the Chinese than was previously contemplated.

Similarly it is surely essential that we move quickly and unambiguously and where it matters and shows to bolster the defense of Pakistan and other countries in the region that are vulnerable and menaced. The time for all that sophistry about whether we have a right or an interest or a justification is reacting at all has long since passed.

The caveats are these: that the president, his advisers and the alliance governments with which we deal should no more react in a thoughtless spasm of anger now than the U.S. should have passed the last few years all too often drowsing like some giant lizard on a rock. Choices require thought and care for consequences and long-term interests, not just short -term satisfaction. The nuclear armament of Pakistan remains, for example, one of the world's worst ideas, no matter what is going on elsewhere in the region, and there is no reason for this country to sell the nuclear pass in relation to the Pakistani government in order to strengthen its conventional defense now.

The SALT treaty and other U.S.-Soviet arrangements also require deliberate sorting out for what we think is vital to preserve -- or at least to preserve an option to resume negotiating. Mr. Carter has to think long. But he also has to make quick, skillful, tough, mean and effective choices now . They will cost us something. Surely the terrible scenes in the Middle East and Central Asia have made plain that Americans are obliged to pay that price.