Fifty thousand Frenchmen turned out for the ceremonies marking the death of Jean-Paul Sartre here the other day. For days thereafter his life and works were the main item on television news and in the daily papers. The three main weeklies -- l'Express, Le Point and Le Nouvel Observateur -- each made him the subject of their cover stories.

Understanding that attention does not come easily to Americans. The central role of the intellectual in France remains a phenomenon beyond the reach of the communications revolution and the comprehension of the celebrity society. So at a time of Atlantic discord, it is more than ever important to grasp the cultural difference.

Sartre made his reputation as a teacher in philosophy. The existentialist creed he preached emphasized that what distinguished man in the world was the capacity -- nay, the unmistakable responsibility -- for moral choice. "Man," he put it, "creates himself by his actions. . . existence precedes essence."

Many Americans who encountered this view, as I did, as students in the early 1950s found the existentialist outlook unimpressive. At best, it seemed a banal statement of the obvious; at worst, a bogus attempt to import drama into the grayness of everyday life.

In retrospect, however, set against the determinist doctrines associated with the names of Freud and Marx, the existentialist view assers itself as a thrust toward freedom and dignity. Along with a burst of economic growth, and the policies embodied by Gen. Charles de Gaulle, it constituted a part of the postwar revival of France.

Besides philosophy, Sartre poured out words in all their other forms. He wrote best-selling novels. He wrote successful plays. He wrote essays on virtually all subjects, and founded an influential literary review. He was, in other words, a complete man of letters. For the France of the 20th century, he filled the role played by Victory Hugo in the 19 the century, and Voltaire in the 18th.

A very special role, because of the nature of French society and politics. The French disease (what snobbism is to the British and guilt is to the Americans) is worship of authority. Whatever the field, whether dress design or wine tasting or administering justice or running the economy, the expert charm of the French is to get on with the powers that be. As a result -- to use Laurence Sterne's famour phrase -- many things are ordered better in France.

But authority, even rational authority, makes mistakes. It compounds injustices and give increase to wrong. So in France to make peace with those in power has been condemned as "the treason of the intellectuals." In France more than anywhere else the office of the intellectual is to stand up for the individual against the state -- to be the battering ram of the adversary culture.

Sartre, in that respect, was a true loyalist. He rejected the Nobel Prize and other honors. He stood up, as many Europeans did not, against the Fascists and the Nazis, and his book on anti-Semitism is a classic. He opposed the Vietnam War -- whether wged by France or the United States. He supported the Algerians in their struggle for independence. His political judgments were not always right. He backed the comunists in France, as the bulwark of working people. For many years he looked away from the murderous police-state features of the Stalinist regime. He ignored the Gulag culture. On that issue, he broke violently with his most celebrated colleague -- the great novelist Albert Camus.

Though he continued to be an uncritical supporter of the left, Sartre came, in the end, to understand the excesses committed in its name. It was right that there should be at his death special tributes from groups of the downtrodden.

But a larger factor, still, entered into the honors paid him on his death. Like many states, France is at once a Catholic country and a nation of unbelievers. Americans think well of Jimmy Carter when he seeks guidance from prayer. If Valery Giscard d'Estaing did it, all of France would roar with derisive contempt. Perhaps especially skeptics need a focus for belief. So the tribute to Sartre shows that even the most sophisticated group in the most wordly of nations has to have a moral guide, a keeper of the conscience.