PARIS -- Incredible! At a time when repression in Cuba hardens and international problems mount, when human rights activists on the island are sentenced to long prison terms and Cubans seek asylum in half a dozen Western embassies -- at just that time -- a popular French novelist, Jean-Edern Halier delivers a paean of praise to Fidel Castro.

Castro, he says, is a ''medieval knight'' whose ''island is too small for him,'' a ''great man'' in a historic role. Cuba itself, he says, exemplifies a kind of ''Russoism,'' with what Jean Paul Sartre once called ''direct democracy and warm lemonade.''

Castro has always had a kind of magnetic appeal for certain writers and intellectuals, especially Europeans and especially the French. He has courted them, read their books and letters, played host to such internationally esteemed writers as Graham Greene and Gabriel Garcia Marquez.

But now the whole world knows the facts on Cuba's political prisons, economic failure, military adventurism and abject dependence on the Soviet Union. Castro's appeal as a charismatic revolutionary leader has waned even as the appeal of revolution itself has dimmed. However, it obviously has not disappeared entirely.

The long interview by Halier in the French Communist daily ''L'Humanite'' demonstrates that, for at least one writer of the Left, Fidel Castro retains his magnetism.

He tells us Castro is a man of ''moving, true simplicity,'' devoted to a life-long ''quest,'' a man ''who questions himself.'' He says Castro is a veritable embodiment of the ''universal spirit of resistance,'' a man ''who has never accepted the discovery that human nature is not good.''

We have heard before testimonials concerning the Caribbean Caudillo, his Russoistic island and his personal charisma. ''If Fidel Castro had not had this charisma for the masses, the arms that he distributed to the people would have been turned against him long ago,'' Halier assures us.

Writers more distinguished than Halier have testified of the attraction felt for remote despots by Western intellectuals who also have insatiable appetites for freedom in their own societies.

This pathology of the Left has been recently reviewed by another French writer, Jeannine Verdes-Leroux, in ''The Moon and the Caudillo'' (Gallimard, 1989). Like the monkeys who hear no evil, see no evil and speak no evil, generations of intellectuals of the Left guarded the Castro myth, testifying in the midst of squalor and tyranny to Castro's solemn commitment ''to give the moon to the Cuban people, if they need it'' (Sartre, 1960).

How could such smart people make such dumb mistakes about a ''liberating'' revolution that has filled Cuba with prisons, driven one Cuban in nine into exile, and has reduced the Cuban Gross National Product from third among the 20 countries of Latin America in 1952 to near the bottom today? The long romance of Western intellectuals with tyrannies still is not fully understood and remains potentially dangerous.

What is it that makes smiling tyrants attractive to free men and women? Is it, as Erich Fromm once argued, that they find freedom too difficult to bear, the multiple choices of democracy too difficult to make? Or is it because of an abiding, unacknowledged hunger for power and the conviction that they know better than the masses themselves what the masses need?

Is this why they find it so difficult to understand George Orwell's fundamental insight about dictatorship and revolution? that power is an end, that one does not establish a dictatorship to make a revolution, but one makes a revolution to establish a dictatorship.

Castro made a revolution and established a dictatorship and claimed the special relationship to history that Halier ascribes to him today. For more than three decades, he has exercised supreme power. He has trained guerrillas from around the world, exported guns, drugs, revolution, and he especially exported uniformed Cubans.

He counted on the Soviet Union and Eastern Europe to provide life's more mundane necessities. When it worked, it worked. As long as the Soviet Union was governed by men chiefly interested in world revolution and military power, Castro prospered -- even if Cubans suffered.

He could count on reliable support from the Soviet Union, Czechoslovakia and the rest of Eastern Europe. Now, with the Soviet Union busy with internal change and Eastern Europe free, about all he can count on from Czechoslovakia is a lecture on human rights.

Fidel Castro thinks he knows all he cares to about how to handle people who raise the issue of human rights -- arrest them, as he did recently when 11 Cuban activists in the Youth Association for the Rights of Man were sentenced to up to 15 years in prison. That's not so bad by Cuban standards. Two political prisoners, workers Mario Chanes de Armas and Ernesto Diaz Rodriquez, have been held in Cuban prisons for 28 and 26 years respectively.

Not many people find Fidel's claims as interesting or as persuasive as they used to. He must have really enjoyed the 10-hour conversation with Jean Edan Halier.