Before the final credits of the documentary “On The Adamant” begin to roll, director Nicolas Philibert can’t help but put in his two cents. “In a world where thinking is often confined to ticking boxes and singularity is stifled,” an intertitle informs us, “some places continue to resist to keep the poetic function of mankind and language alive.”

Mr. Philibert has made a good, sometimes disturbing, and often moving film about mental illness. The individuals on whom he has trained his camera are involved in creative therapies — music and painting, largely — and the director is, for the most part, hands-off as a documentarian. The film is blessedly free of talking heads.

Yet when he adds that postscript about poetry, singularity, and, by fiat, the authenticity of the outsider’s vision, Mr. Philibert stoops to romanticizing affliction. It’s worth recalling that Van Gogh’s greatest paintings are not markers of psychological distress but proof that it can be clarified and transcended. We condescend to the mentally ill by treating their maladies as markers of genius.

Van Gogh comes up during “On The Adamant,” and in terms that will likely give viewers pause. One of the subjects of Mr. Phiilbert’s film, Frederic, tells of a Byzantine conspiracy that involves “that devil, that rascal” Wim Wenders. The German filmmaker has, you see, transformed both Frederic and his brother into the “reincarnation of Theo and Vincent [Van Gogh] … transposed into Reagan’s America.” The means by which Mr. Wenders did so was his 1984 movie, “Paris Texas.”

Frederic is capable of moments approaching the pellucid. After extolling the virtues of Jean Gabin, Louis de Funès, and Lino Venturi — Frederic is an old school movie buff — he starts to wax philosophical about the patients on board the Adamant: “You have actors in here who don’t know they’re actors. It’s not medical. They’re actors without realizing.” Which is, in the end, not an altogether inappropriate point of reference for the range of folks we meet in Mr. Philibert’s picture. 

The Adamant is a large wooden structure planted on a barge docked in the Seine, just a short jaunt from the Gare de Lyon train station. Docked, that is, and stationary: this is a daycare facility for adults with mental illness. Established by the Paris Central Psychiatric Group in 2010, the Adamant serves citizens from the French capital’s first four arrondissements. The site provides medical assistance and aims to foster a sense of community.

The occupants of the Adamant are allowed to state their pieces through the gentle prompting of off-camera questions or scenes centered around group activities. The weekly accounting sessions for the on-board coffee and snack bar punctuate the proceedings regularly enough to give the film’s freeform structure a sense of grounding. The accumulation of discrete moments featuring this-or-that individual allows for insight into the lives and struggles of the Adamant’s guests.

The film begins with a spectacular cold-opening: An Adamant regular, François, performs a song by 1970s French rock band Téléphone, “The Human Bomb.” What begins as a by-the-book recital turns into a spiritual purgative: The number is sung with a conviction that speaks less of Top Forty nostalgia than foundational human truths. 

We later re-encounter François as he explains the relative merits of medication, therapy, and life on the Adamant. It is within such starkly configured moments that “On the Adamant” proves its mettle, not as a starry-eye polemic but as a meditation on the frailties of the human animal.