A film by … who? Though the fury — usually spurred by screenwriters — over that pesky creature known as the possessory credit has calmed a bit, it remains a complicated topic that can stir up as much argument as can be found inside an Iowa caucus group.

In one corner are directors who are perfectly happy (as far as we know) directing. Period. Their latest films, awards contenders all, don’t send off the whiff of bland collaboration made by an industrial machine, but rather hit the viewer with the strong imprint of an artist at work — alongside others, including the screenwriter.

  • In “Zodiac,” director David Fincher immediately establishes a tone of obsession, dread and a strange tension between the sheer drudgery of investigative journalists and cops at work and the furtive horrors of a serial killer. He does this in the context of, first, a script by James Vanderbilt, who in turn adapted Robert Graysmith’s fact-filled books “Zodiac” and “Zodiac Unmasked.”

  • Sidney Lumet, whose working methods derive from the theater where the playwright holds sway, allows writer Kelly Masterson’s voice and Cartesian sense of storytelling structure to dominate “Before the Devil Knows You’re Dead.”

  • Like “Zodiac,” “The Diving Bell and the Butterfly” is a case of a tome (by Jean-Dominique Bauby) derived from personal experience, then adapted by Ronald Harwood, and then directed by Julian Schnabel in a way that the fingerprints of a literary adaptation are nearly invisible.

  • No musical author rules his form like Stephen Sondheim, but the evidence onscreen of “Sweeney Todd: The Demon Barber of Fleet Street” is of a stage work respectfully treated by director Tim Burton, yet molded to Burton’s particular tastes — which translates as more Gothic extremism, less Broadway comedy.

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In another corner are writer-directors who tend to view the filmmaking process as a continual flow from the page to the camera to the editing room, guided in principle by a single intention. Four of the more striking cases among the contenders happen — ironically enough — to be based on books, or, in the case of Todd Haynes’ “I’m Not There,” a Baroquely imaginative retelling of Bob Dylan’s life with six Dylans played by six actors, and beyond that, a life often told in free association and far from chronological order.

Paul Thomas Anderson’s “There Will Be Blood” (selectively adapting from Upton Sinclair’s novel “Oil!”) and Sean Penn’s “Into the Wild” (religiously adapting Jon Krakauer’s book) emerge as films that are so personally shaped and built — both viewing the West with intensely cinematic means as a land of endless dreams and bottomless threats — that it’s impossible to imagine that the books could have been filmed in any other manner.

  • The usual presence of pure evil that stalks many of Joel and Ethan Coen’s movies — from “Blood Simple” to “The Ladykillers” — also rumbles through “No Country for Old Men,” with a storytelling tone and template from novelist Cormac McCarthy that drains the film of any of the snide cleverness that often seeps into the brothers’ work.

Seen together, these movies can buttress either side of the film-by-whom? argument. Hollywood traditionalists who prefer clear job delineations and despise the auteur theory (which Lumet rather intemperately terms as “nonsense” in his book “Making Movies”) will point to “Zodiac” or “Devil” as proof that great movies can still be made by separate writers and directors. Yet “Zodiac” is unmistakably a case of Fincher revisiting the territory of his “Seven” and plumbing considerably richer thematic veins that extend far beyond genre, and “Devil” is an almost ideal melding of Lumet’s version of Eugene O’Neill’s definitive family tragedy “Long Day’s Journey into Night,” with the tick-tick-ticking doom of “Dog Day Afternoon.”

It’s also a glaring yet oft-repeated fallacy that the durable auteur theory first advanced by the 20th century’s greatest film critic, Andre Bazin, applies somehow only to writer-directors.

In fact, Bazin looked to (among others) the American films of Howard Hawks and Alfred Hitchcock laboring in the once-rigid studio system for signs of direct authorship onscreen, seen especially in the ways that the demands of genres were sculpted by Hawks and Hitchcock to their own ends — a notion furthered by Alexandre Astruc and his theme of “camera-stylo” — literally, the camera as pen.

Conversely, is a motion picture like Penn’s at all possible without the original voice of Krakauer, whom Penn has gone out of his way to praise as the key to “Into the Wild” being a movie? Perhaps not, but the film’s almost terrifying will to burrow inside the mind of young Christopher McCandless as he ventures off modernity’s grid is in brotherhood with Penn’s uncompromising earlier films “The Pledge” and “The Indian Runner,” which first indicated that, yes, here was an auteur.

And speaking of terror, those frightened eyes of audience members after guild screenings of “There Will Be Blood” are just one sign that the shock of the new — which Anderson’s film emphatically delivers more than any other American movie this past year — is perhaps most muscularly created by a single and single-minded artist operating with freedom, but also with the same rigor and individual voice that made possible “Hard Eight,” “Boogie Nights,” “Magnolia” and “Punch-Drunk Love.”