IT'S JUST as well that the sentimental vision of Soviet-American relations that President Reagan offered in his pre-summit address is not central to his actual policy. The vision of ordinary people going back and forth nourishing each other's understanding has little to do with reducing what the president otherwise plainly understands as the real conflicts of interest and outlook between the two powers.

Whether it's wise to invest much hope in building these citizen bridges -- which are usually the first to crash when a regional or political dispute erupts -- before any of the disputes are treated is a question. Some of the exchanges Mr. Reagan would now resume were suspended after the Soviet invasion of Afghanistan, which continues. The vision does, however, reflect American good will.

The president's sudden embrace of exchanges is dismissed in skeptical quarters as an effort to ensure that he has something to bring back from a summit that otherwise promises only limited tangible results. But it may make more sense to see the proposal as a broad-screen projection of his belief in the potential of the leader-to-leader exchange that he is conducting himself.

Mr. Reagan seems to feel that by vigorous exposition he can break through some of the unfounded distrust to which he attributes Soviet policy differences. Few would underestimate his talent for one-on-one engagement. Still, he would be breaking new summit ground if he were to alter his Soviet counterpart's world view. The more realistic Geneva goal, and one whose modesty and subjectivity require no apologies in a world of nuclear weapons, is simply to raise somewhat the level of mutual understanding.

To get an impatient public off its back, the administration has discouraged expectations of progress on arms control, the one major area where accord is conceivably within reach. Yet it does not seem unreasonable to hope that Mr. Reagan and Mr. Gorbachev can come to broad terms. The first requirement is to halt the rotting of the existing arms control framework caused by Soviet noncompliance and American distancing, and the second requirement is to move on from there.

Thanks in part to Ronald Reagan, the United States has gained back much of the general strategic momentum, which should translate into bargaining confidence, that it lost in the 1970s. The Soviets will not pay exorbitantly for, but perhaps could use, something of a breather. Therein lies the possibility that Moscow will put on the table the disproportionate offensive capacity that has come to trouble the United States so deeply, and Washington will put on the table the pursuit of early unilateral deployment of a high-tech defense. That is what any serious arms control bargaining will be about. Whether or not it comes to anything, Mr. Reagan has created the conditions to make it at least possible.