At the third annual Allard K. Lowenstein Seminar, to mark and celebrate the gift of the late political activist's papers to the University of North Carolina library, a bizarre rumor suddenly spread. On Sunday, someone had heard, a New York Times poll would show that 10 years after the fall of Saigon (April 1975) the Vietnam War is for most Americans a nearly forgotten episode -- "as obscure as the Wars of the Roses," as someone put it.

The rumor turned out to be a bit exaggerated, though only a bit. What the Times poll actually discovered, wrote Adam Clymer in the paper's Sunday magazine, "is how little many in the United States know, or are willing to remember, of the searing . . . war." Only three of five, for instance, could say whose side the United States had fought on.

At a seminar memorializing a man who had cared so passionately about the war and other great issues, it was the crowning irony, the ultimate expression of national amnesia. A great deal -- maybe too much, too soon -- has been said of what we ought to remember about Vietnam. But if this poll is right, perhaps the greatest lesson of all is the power over our memories of what psychologists call "denial": the inability to accept unpleasant realities.

Allard Lowenstein, murdered five years ago by a demented follower, had been in 1968 the grand strategist of the so-called "Dump Johnson" movement, the culmination of the first phase of the anti-war movement. Al had given us Eugene McCarthy and the "kids," which was afterward joined by Robert Kennedy's insurgency. It was a gauge of his passionate views.

But the perverse end of the enterprise was not the end of the war but the election of Richard Nixon. From the peace activist's point of view, Nixon's end-the-war program after January 1969 (which more than doubled both the bombing of North Vietnam and the U.S. casualty lists) became a classic illustration of the nemesis of political protest. Al Lowenstein, a resilient spirit, was probably undaunted by this ironic turn of events. As Churchill says somewhere, politics is always an act of faith, never guaranteed to turn out right.

But what about the news that three of five Americans have forgotten, or are reluctant to recall, even whose side we were fighting on? This is disturbing in a very different, and somehow worse, way.

What would Al say? It is all speculation, of course. His views were in the best sense unpredictable. But from what was remembered of him by his friends, associates and admirers last weekend, it wasn't hard to guess that he would be appalled by evasion and forgetfulness. He probably would go so far as to say that it is better, even, to be wrong than to be so indifferent to a traumatic American encounter wih history that shaped, and goes on shaping, our sense of our responsibilities as a world power.

Forget Vietnam? Consign it to the dim attic of memory with the Wars of the Roses? Some of us could hear Lowenstein asking the question that must always be asked: What does a nation have if it has no memory and therefore, most likely, no sense of where it is going now?