Even as the documentary genre becomes more inventive, it still faces the same old dilemma: how to keep an audience from drifting off while watching a film about some urgent reality. And also how to do so without making it hard for them to sleep at night.

Portuguese filmmaker Miguel Gomes addresses that issue up front in his six-hour-long “The ‘Arabian Nights’ Trilogy,’’ screening at the Harvard Film Archive Jan. 14-23. At the beginning of “Volume 1, The Restless One,’’ during a collage sequence about a shut-down Lisbon shipyard and a plague of Asian hornets that are killing off the local bee population, Gomes addresses the audience directly.

He confesses he can’t conjure up a link between the two events. He wants to make a film that is both fantastic and realistic, but his imagination — and conscience — prevent him.

Then he runs away.

He has reversed the approach of Michael Moore, who sticks around and peppers his screed with sometimes funny satire. Instead, Gomes engages the services of Scheherazade (Crista Alfaiate), narrator of the ancient compendium of fantastic tales, “The Arabian Nights,’’ to lend a hand.

As in the original, to avoid the fate of her beheaded predecessors, Scheherazade must regale her husband, the king, with a tale started at nightfall and left unfinished at dawn, forcing him to stay her execution until he hears the end — at which point she starts another that piques his interest. Stories, it seems — the more fantastic the better — are the only way for the powerless to confront absolute power.

And so, in a kind of magic neorealism, Gomes interjects the fabulist world of genies, wizards, heroes, and thieves into true stories of the straitened lives of people suffering from — as the opening title of each film puts it — “a program of economic austerity executed by a government apparently devoid of social justice.’’

Some tales work better than others — the further the fantasy strays from the didactic and tends toward the non sequiturs and silliness, the better. In “Volume 1,’’ a story with an unprintable title features a wizard who recognizes that the international money people are mean-spirited because they suffer from erectile dysfunction. Presto! Portugal’s debt is forgiven. But sometimes one can have too much of a good thing. On the serious side, the hourlong “The Inebriating Chorus of the Chaffinches’’ that dominates “Volume 3’’ is basically a generic documentary with Scheherazade’s commentary appearing in text like balloons from VH1’s “Pop-Up Videos.’’ It might prove a long haul even for birders.

If you only have time for one film, I’d recommend “Volume 2, The Desolate One.’’ Especially affecting is the Buñuelian “The Tears of a Judge.’’ A naked woman, on the phone to her mother, discusses her success at losing her virginity. A cut is made to the mother, who presides in a court set up in an outdoor forum, a scenario not unlike Q judging the human race in the “Star Trek: The Next Generation’’ episode “Encounter at Farpoint.’’

Those accused are summoned to testify, confessing to crimes and implicating others in misdeeds of increasing absurdity. Finally the judge can’t take any more. The tears she sheds are real.

Peter Keough can be reached at petervkeough@gmail.com.