If you think of great libraries as archives of the human condition, maintained to preserve everything we’ve thought and done, then you’d figure Frederick Wiseman would eventually make a film about the New York Public Library. He, too, carries the totalizing virus.

Over the course of a 50-year career, Wiseman has sought to capture the living essence of an entire world’s worth of institutions—from madhouses and wards for the terminally ill to great theater companies, universities, and ballet schools; from welfare offices, zoos, and meatpacking plants to nuclear-weapons training facilities, art museums, state legislatures, and Central Park. At his most optimistic, he turns his attention to towns or neighborhoods where he sees multiple forces interacting for the common good: in Belfast, Maine, or the Jackson Heights section of Queens, New York. At his most scathing—in Public Housing, for example—the institutions he studies seem almost deliberately constructed to make people fall apart.

Look at libraries differently, though—as providers of services to the urban masses—and it will seem just as inevitable that Wiseman would get around to them. He, too, is an agent of social change. The title of “muckraker” is, of course, too simple for him, despite the scandal of his first films: Titicut Follies (1967), which the State of Massachusetts tried to ban from public view, and High School (1968), which, in the words of one reviewer, showed the systematic conversion of “warm, breathing teenagers” into “forty-year-old mental eunuchs.”

Still, just as an activist streak runs through the branches of the New York Public Library, so too does it animate all but Wiseman’s most contemplative works. He is, famously, an observational filmmaker, who refuses to conduct interviews, add explanatory texts or voice-overs to the image, layer extraneous music onto his scenes, or even provide a caption to tell you who’s talking. You get nothing except what you would have seen and heard if you’d been present with him when the action was happening. And yet, through his choice of what material to show and how to sequence it, he often constructs implicit arguments that address not so much the arrogance of power as its mindless, grinding indifference. These implied polemics are all the more persuasive for seeming to emerge from the evidence before you.

In his 42nd film, Ex Libris: The New York Public Library, which receives its theatrical premiere in September at Film Forum in New York, Wiseman looks at his subject from both his Olympian and activist perspectives, and with attention to both major aspects of the NYPL’s mission: a center for scholarship and a resource for the city’s poor, ill-schooled, and homeless. Following an organizing scheme he’s used before, Wiseman bounces back and forth in his scenes between the marble palace on Fifth Avenue and a scattering of humble branch libraries in the Bronx and Harlem; public events and back-of-the-house labor; executives planning the system’s future and ordinary people using what the NYPL offers.

Pay attention to context and do a little Internet research, and you can find out that the uncaptioned decision makers overheard in their deliberations are NYPL president Tony Marx, chief library officer Mary Lee Kennedy (who has moved on since the film was shot), chief operating officer Iris Weinshall, and vice president for government and community affairs George Mihaltses. I identify them here to make the point that Wiseman had access to serious people talking about critical issues. He also had access to many anonymous members of the rank and file to whom these leaders are responsible, including toddlers singing “Old MacDonald” at story time, kids doing homework and building robots after school, a researcher combing through Timothy Leary’s correspondence in the manuscript room, career-seekers at a jobs fair, and an elderly woman in Chinatown learning to use a computer.

Negotiating between these two groups, and sparking the movie to emotional life, are the heroes of Ex Libris: librarians. Some of them come before you as marvels of patience and dry humor. A reference librarian on the phone desk calmly informs a caller that unicorns are actually imaginary; an after-school-program librarian in the Bronx advises a kid, “If you’re holding onto the robot to make it stop moving, then that means you need to change something on the computer.” Others are bearers of infectious enthusiasm. They boast to visiting students that in the picture collection, you can look up subjects such as “dogs in action”; they proudly show off an Albrecht Dürer print of a rhinoceros, while explaining that in the early 16th century, this treasured item was a kind of newspaper. Most crucially for the tone of Ex Libris, the librarians offer care and warmth, whether they’re doling out picture books to the schoolkids who squirm around them or distributing Wi-Fi boxes, with a sincere “Congratulations,” to a line of West Harlem residents who have qualified for the free rental.

I pause to note that Wiseman could have put other librarians on the screen had he wanted to—the ones, for example, who have kept me waiting 40 minutes for a book that turned out to have gone missing, and then tossed back the call slip as if they were flipping the bird. But they wouldn’t have suited the theme he has in mind for Ex Libris.

More a collage artist than an investigative reporter, more a phenomenologist than a historian, Wiseman has given a much different treatment of the NYPL than you would find, say, in Scott Sherman’s book Patience and Fortitude (written in part for The Nation, and published in 2015 just before Ex Libris went into production). Wiseman is interested in librarians as wonderful people—as comfortable making an impromptu translation from Middle English (while denying that they’re good at it) as they are teaching a blind person to read Braille, or directing a woman to copies of steamship manifests so she can trace her family’s arrival in America. He has edited Ex Libris to suggest two broad questions about these multitalented public servants: How does the NYPL keep the librarians working? And what is the broader meaning of what they do?

The answer to the first question comes in the scenes of library president Marx and his executive crew and can be summed up in one word: money. Ex Libris is in some ways an essay on fund-raising, or (to be more precise) the interplay between public allocations and private philanthropy. The first time you see Marx, he’s giving a talk on this subject to library supporters, using the example of the NYPL’s digital-access initiative to illustrate how donations pouring in from one source can uncork funds from the other. The last time you see him—some three hours later in the film’s running time—he’s in his conference room, planning how to keep the money flowing toward the NYPL in the city government’s next budget. The challenge, he says, is to match the language of solicitations to the NYPL’s goals. The big, simple message for donors must somehow reflect the priorities the library has set for meeting the public’s needs.

You hear a lot in the conference room about those needs in their immediate and practical form. The agenda includes providing a reasonable degree of daytime shelter for people who live on the streets (“The library is a place where we don’t keep our distance from the homeless,” Marx tells his colleagues), making up for deferred maintenance in the branches, and balancing the money spent on books that the general public wants today with the cost of books that will be useful in the future. But the larger meaning of the institution’s role emerges elsewhere: in scenes of the library’s public programs of interviews, lectures, and discussions. Here again Wiseman had a wide choice of moments to include. He selected those that suggest the most radical agenda.

Ex Libris begins with a long excerpt from a book talk with the scientist and secularist Richard Dawkins. (All excerpts from the public programs are long. Wiseman, as usual, is in no hurry in this film; he believes ideas need time to develop.) Calling for nonreligious people to make themselves heard, Dawkins insists that some ideas are simply not true—the theories of young-earth believers, for example—and must be labeled as such. As for the supposed absence of awe and wonder from atheists’ lives, he says that nothing could be more moving than to contemplate the reality of a living cell, in all its stupefying complexity.

And so, by borrowing Dawkins’s words, Wiseman suggests the terms that will describe the NYPL through the rest of the movie. The institution is thrilling in its complexity and resolute in its service to the truth. The complexity of the library’s operations is, of course, seen everywhere in Ex Libris. But when it comes to the issue of propagating the truth, Wiseman has decided to focus on one fact among all the others that the library addresses: the continuing legacy of slavery.

By the time Ex Libris is over, you’ve heard about opposition to the slave trade by 17th-century Muslim clerics in Africa and the defense of slavery by writers in the antebellum South. You’ve listened to Ta-Nehisi Coates talk about his family’s reverence for Malcolm X, and have sat in on a discussion held in a tiny branch library between Khalil Gibran Muhammad (at the time director of the NYPL’s Schomburg Center, and a current member of The Nation’s editorial board) and people outraged over McGraw-Hill’s whitewashing of slavery in recent textbooks. When you see a performing-arts workshop on sign-language interpretation for the deaf, the text being used for illustration is the Declaration of Independence. When you peek into a meeting of the board of trustees, Kwame Anthony Appiah is giving a presentation about the works of Phillis Wheatley.

For Wiseman, this is where the scholarly and social missions of the library intersect: in speaking the truth about slavery and its aftermath, while providing services in many neighborhoods where people still bear the marks of slavery’s more obvious burdens. He gives a very fine-grained picture of the library in this dual role, neither ignoring the day-to-day operations of the NYPL system nor neglecting the beauty and delight of its collections and magnificent main building. There is so much beauty and delight in Ex Libris, in fact, and so much vivid personality in all the people, that a lackadaisical viewer could be excused for summing up the film as a loving tribute. So it is, I suppose. But even at age 87, there is nothing lackadaisical about Wiseman. The sly old wizard constructs a top hat right before your eyes—and then, while you’re admiring its sheen, pulls out a 500-year-old rabbit.

Theo Anthony was born in 1989, about 60 years after Frederick Wiseman came into the world, and until recently had made only a few short documentaries. You wouldn’t want to curse him with high expectations for his first feature-length documentary, especially when he’s given it the sure-to-please title Rat Film. But the deliberately strange essay he’s composed—on what you might call the natural history of racism—is so inventive and, appropriately, so biting that he’ll have to get used to being praised.

Unlike Wiseman, Anthony revels in voice-overs, soundtrack music, informative text overlays, and on-camera interviews, especially when they come at you from unexpected angles. Before you can get your bearings in Rat Film, a voice has recited a series of mock-academic titles (“Presentation of a Video Game,” “Explanation of an Experiment”); the exhaust-pipe flames of a drag racer have erupted in slow motion; a string quartet has played something inappropriately meditative; and the head of a snake has briefly ventured across a corner of the screen. Meanwhile, the ostensible subject of this documentary—rats in Baltimore—has not yet come into focus. Fuzzy video, shot in an alley at night, looks down at a rat trapped in a garbage can. The average Norway rat, the mock-academic voice informs you, can jump 32 inches, whereas the regulation height of a Baltimore garbage can is 34. (Is this true? I don’t know.) At last the picture sharpens, and you see the rat clearly, its eyes shining furiously in the dark.

Having unbalanced you, Anthony proceeds to go backward in time and simultaneously outward into Baltimore’s neighborhoods. Backward: to a history of city ordinances, housing covenants, and bank-loan policies that confined African Americans to wretched slums; to the declaration, during World War II, of a war on rats, conducted with poison in these same slums; and to the writings of a prominent Johns Hopkins scientist who didn’t draw much of a distinction between the rats and the slum dwellers. Outward: to the backyards and alleyways today where some Baltimore residents hunt rats for sport (with tools including blowguns and a rod-and-reel), and where a chatty, philosophical pest-control officer makes his rounds. Baltimore has never had a rat problem, he declares; it has always been a people problem. He likes rats—they put food on his table.

Rat Film is a movie for people who feel that the world we’ve made is so unbelievably outrageous that it can best be conveyed in a scramble. Viewers who demand a point-by-point exposition will not be happy. The rest of us can hang on for the ride.