Horrible visions of the future are a staple of movies, but the future vision depicted in “Ghost in the Shell,” based on the Japanese comic book, is more dispiriting than most because it’s more than plausible. It’s practically inevitable. While watching, the question that keeps crossing the mind is how do we prevent this? But the question has no answer.

The movie’s title refers to a situation in which a human spirit is housed in a synthetic body. In “Ghost in the Shell,” most human beings are no longer entirely human but combinations of flesh and machine. There are replacement limbs and replacement eyes, of course, but there are also brain enhancements, such as chips that allow a person to learn French in one minute. Scarlett Johansson plays the ultimate end-product of this process — a human brain housed in a completely synthetic, human-like body.

The existence of such an individual has implications that touch all aspects of life. What is a human being? What is a human spirit? And who owns the life-giving technology, and how can it be abused? “Ghost in the Shell” devises plenty of reasons for action scenes, most of them good reasons, but the action doesn’t overwhelm it. This is a thoughtful movie that’s interesting now and will probably still be interesting in 100 years, whichever way things go.

Directed by Rupert Sanders (“Snow White and the Huntsman”), it takes place in what seems like a futuristic Tokyo, in which the skyline is filled not only with buildings but with weird building-sized holographs — ominous, smiling figures that are probably advertisements. Throughout there is a sense of a squalid, frenetic world in which monstrous businesses are in a constant effort to sell things, even though hardly anybody has any money.

As a cyborg, Major (Johansson) has been designed to fight terrorism. She is essentially a super-charged cop, in possession of great speed and powers of climbing and leaping. She works directly under a government minister played by Takeshi Kitano, the action star and director. And for routine maintenance, repairs and downloads, she sees the scientist who helped create her, Dr. Ouelet (Juliette Binoche), who takes a personal interest in her welfare.

For Johansson, “Ghost in the Shell” isn’t much of an acting challenge, except perhaps as a physical role. The movie calls for her to be mostly in a state of confusion or dim apprehension, but she helps serve up scenes for others. Even if you don’t know Kitano’s pedigree one of the world’s greatest action stars, you can tell just from his quizzical and assured expression that sooner or later he will explode. Binoche brings an arresting quality to her role — a reassuring serenity with an undertone of anxiety, as if questioning the moral underpinnings of her life, her work and her world.

And one of the best scenes in the entire film is a quiet interlude between a fairly blank Major and a motherly Japanese woman who spontaneously invites her in for tea. Something about the performance of the actress, Kaori Momoi, is extraordinary. Though performing in a language she can barely speak, she brings to the scene a complicated dynamic in which several things seem to be happening at once, all of it beneath the surface.

Yet oddly, about a third of the way into “Ghost in the Shell,” it seems like it might derail. After giving us a character whose very existence presents a fascinating moral proposition, the movie seems to shift gears. It stops focusing on the world of the film and starts concentrating on more garden-variety issues such as deception and betrayal. But the movie is more deft than you might expect, and this unwelcome detour ultimately turns into a way for the filmmakers to dig deeper into the movie’s real issues, such as what is life and what it all means.

“Ghost in the Shell” is like an amalgam of 2017 anxieties. Fear of technology. Fear of big business. Fear of being spied upon. Fear of the sacred disappearing, and of the crass, the loud and the empty crowding into every corner of existence — crowding out life itself. But the movie doesn’t just exploit these fears. It communicates an idea that may turn out to be important, that sooner or later, we as a species are going to have to decide about the limits of technology. And the limit may have to be the human brain.

Mick LaSalle is The San Francisco Chronicle’s movie critic.

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