After the image of a Brooklyn student named Vidal captured widespread attention on the Humans of New York blog, he and the photographer, Brandon Stanton, were invited to the White House. PHOTOGRAPH BY BRANDON STANTON. COURTESY ST. MARTIN’S PRESS

The most famous photograph from Brandon Stanton’s new book, “Humans of New York: Stories”—the one you have probably seen or read about or heard discussed—is of a boy in an open black bubble jacket. Beneath the jacket is a fleece-lined hoodie, also black, and in his hand the boy holds a black plastic bag, stretched by the weight of what might be groceries. The sidewalk behind him is cracked and dotted with litter. Dull-brown public-housing towers—as much a part of the quintessential visual New York as the bodega bag—form a jagged horizon.

You might know that this boy’s name is Vidal, and that he attends the Mott Hall Bridges Academy, in Brownsville, and that images of him, the first of which was accompanied by the somewhat noirish details of his still-short experience (“When I was nine, I saw a guy get pushed off the roof of that building right there,” he says), became widely shared sensations on Stanton’s Humans of New York blog and its attendant social-media channels earlier this year. The world learned that the most influential person in Vidal’s life was Nadia Lopez, his principal at Mott Hall, and, after subsequent HONY posts featuring Lopez, marvelled at her admirable devotion, amid the imagined grayscale of still-ungentrified Brooklyn, to boosting the spirits, and lifting the ambitions, of her students. Sensing an uncommon interest in Vidal among his audience, Stanton launched a fund-raising campaign that yielded an eventual $1.4 million for the school. In February, as a coda, Vidal and Lopez met President Obama, in the Oval Office. In Stanton’s photo of the encounter, Vidal sits grinning behind the Resolute desk, the President and principal flanking him like wings.

This series of events—Vidal’s travel, in the reckoning of HONY’s devotees, from photograph to popular phenomenon—is in many ways a perfect realization of the ethos of “Stories,” which recently débuted at No. 1 on the New York Times best-sellers list. In his introduction to the book, which doubles as a statement of purpose for HONY now and into the future, Stanton describes the process by which the project “evolved from a photography blog to a storytelling blog.” (Stanton, who grew up in Georgia and briefly worked as a bond trader, started Humans of New York almost immediately after arriving in New York City, for the first time, in his mid-twenties.) The short and notionally revealing quotes that accompany each image “grew longer and longer,” Stanton explains, “until eventually I was spending fifteen to twenty minutes interviewing each person I photographed. … The blog became dedicated to telling the stories of strangers on the street.” “Stories,” then, is an effort to mirror “the in-depth storytelling that the blog is known for today.”

In this way, HONY joins organizations like TED and the Moth at the vanguard of a slow but certain lexical refashioning. Once an arrangement of events, real or invented, organized with the intent of placing a dagger—artistic, intellectual, moral—between the ribs of a listener or reader, a story has lately become a glossier, less thrilling thing: a burst of pathos, a revelation without a veil to pull away. “Storytelling,” in this parlance, is best employed in the service of illuminating business principles, or selling tickets to non-profit galas, or winning contests.

Photography has long been used instrumentally, if not to tell stories in this contemporary sense, certainly to call attention to various social realities. The reformist journalist Jacob Riis, for example, used photographs—collected in books like “How the Other Half Lives”—to uncover the squalor of late-nineteenth-century tenement life on the Lower East Side, along the way becoming an innovator in the use of flash photography. But, rather than pithy quotes or even harrowing anecdotes, the accompanying writing was deep and skillfully rendered reportage, connected chiefly by implication to the pictures Riis had taken. Thus occupying the vague space between archetype and anecdote, between the particular and the more broadly illustrative, Riis’s photos realized photography’s unique and enduring possibility—to serve artistic and documentary ends at once.

This is how, when observing a photograph of three children asleep on the street, we experience a kind of moral-aesthetic double vision: we feel the injustice and brutality of the thing itself, for these three and others facing a similar plight, and, at the same time, marvel at Riis’s ability to mythologize them, making each an avatar of bravery, of camaraderie, of love.

It might be instructive to consider Stanton’s photo of Vidal along similar lines, sans story. Forget, for a moment, the factual details that we have gathered in the course of knowing-but-not-really-knowing him: the aerial murder; the school so suddenly flush; the audience with the leader of the free world. Forget his name, even. Consider, instead, the ease of the boy’s sneakers against the sidewalk; his shy, smirking confidence; the preternatural calm with which he occupies the space within the frame. Viewed like this—as, yes, irrefutably real, but also as a readable image—he is reminiscent of Gordon Parks’s squinting Harlem newsboy. Both convey something almost spiritual: something about the delicate string that hangs between youth and resilience, about the miraculous talent of children, however voiceless, to stand unswallowed by the city.

During the throes of the Great Depression, the novelist Erskine Caldwell and the photographer Margaret Bourke-White travelled together through the rural South, hoping to gather impressions from the lives of black and white tenant farmers. The resulting book, “You Have Seen Their Faces,” might be read as a direct ancestor to HONY: each of Bourke-White’s photographs is a melodrama in black and white, adorned with an illustrative caption. A barefoot black boy in East Feliciana Parish, Louisiana, stands surrounded by newsprint-papered walls, a dog at his feet. “Blackie ain’t good for nothing,” the caption says. “He’s just an old hound dog.” A white man, jowly, with round glasses, gazes skyward: “Beat a dog and he’ll obey you. They say it’s the same way with the blacks.”

Like Riis, Caldwell and Bourke-White had explicitly political reasons for undertaking their project, involving the periodically necessary task of introducing America to itself. Hence the grammar of the title: You, presumably a Northern, urban liberal, well-meaning but essentially ignorant of the lives of your poor southerly neighbors, are now invited to partake in Their hardships. And—again, as with Riis—this acquaintance is earned by way of more than pictures and homespun snippets: the pages of “You Have Seen Their Faces” are split almost evenly between text and image; Caldwell goes on at length, magisterial and morally devastated at turns, providing a real accounting of American exploitation, and of its casualties. It is not, Bourke-White and Caldwell seem to say, enough simply to see the faces of one’s destitute countrymen. Instead, the collision of photograph and paragraph requires a constant movement between broad themes and searing details, between sentiment and cold fact.

“You Have Seen Their Faces” presents the challenge of knowing other people as possible, if only gradually, and after an acknowledgement of social and racial distances. Another hybrid text of the era, James Agee and Walker Evans’s “Let Us Now Praise Famous Men,” regards the entire enterprise with something like despair. To the extent that “Famous Men” has an overriding agenda, it is to arrive at a sense of the dignity—or, perhaps, even more simply, the reality—of others, despite the stubborn mystery of their circumstances. This might explain the vast expanse of interpretive space between the book’s images and text: Evans’s photos sit alone at the front of the book, unremarked upon, serving as a kind of tonal prelude, then cede the stage completely to Agee’s wild, modernistic jumble of verse, prose, and theatric convention. If there are connections to be made between the photos and the words, they are left untraced, leaving crucial labor to be done by readers—involving and implicating them in an important, if impossible, process of discovery.

Agee is at times almost mischievous in his illustration of the unknowability of other people and their problems—and the moral quandary involved in trying to uncover them anyway. In his listing of the dramatis personae in “Let Us Now Praise Famous Men,” he catalogues himself and Walker ruefully: