The congested-megalopolis sets are extraordinary, and they’re lovingly, perhaps obsessively, detailed; this is the future as a black market, made up of scrambled sordid aspects of the past—Chinatown, the Casbah, and Times Square, with an enormous, mesmerizing ad for Coca-Cola, and Art Deco neon signs everywhere, in a blur of languages. “Blade Runner,” which cost thirty million dollars, has its own look, and a visionary sci-fi movie that has its own look can’t be ignored—it has its place in film history. But we’re always aware of the sets as sets, partly because although the impasto of decay is fascinating, what we see doesn’t mean anything to us. (It’s 2019 back lot.) Ridley Scott isn’t great on mise en scène—we’re never sure exactly what part of the city we’re in, or where it is in relation to the scene before and the scene after. (Scott seems to be trapped in his own alleyways, without a map.) And we’re not caught up in the pulpy suspense plot, which involves the hero, Deckard (Harrison Ford), a former blade runner forced to come back to hunt down four murderous replicants who have blended into the swarming street life. (The term “blade runner” actually comes from the title of a William Burroughs novel, which has no connection with the movie.) It’s a very strange tenderloin that Ridley Scott and his associates have concocted; except for Deckard and stray Hari Krishna-ites and porcupine-headed punks, there are few Caucasians (and not many blacks, either). The population seems to be almost entirely ethnic—poor, hustling Asians and assorted foreigners, who are made to seem not quite degenerate, perhaps, but oddly subhuman. They’re all selling, dealing, struggling to get along; they never look up—they’re intent on what they’re involved in, like slot-machine zealots in Vegas. You know that Deckard is a breed apart, because he’s the only one you see who reads a newspaper. Nothing much is explained (except in that opening crawl), but we get the vague impression that the more prosperous, clean-cut types have gone off-world to some Scarsdale in space.

Here we are—only forty years from now—in a horrible electronic slum, and “Blade Runner” never asks, “How did this happen?” The picture treats this grimy, retrograde future as a given—a foregone conclusion, which we’re not meant to question. The presumption is that man is now fully realized as a spoiler of the earth. The sci-fi movies of the past were often utopian or cautionary; this film seems indifferent, blasé, and maybe, like some of the people in the audience, a little pleased by this view of a medieval future—satisfied in a slightly vengeful way. There’s a subject, though, lurking around the comic-strip edges: What does it mean to be human? Tracking down the replicants, who are assumed not to have any feelings, Deckard finds not only that they suffer and passionately want to live but that they are capable of acts of generosity. They have become far more human than the scavenging people left on Earth. Maybe Scott and the scriptwriters (Hampton Fancher and David Peoples), who adapted the 1968 novel “Do Androids Dream of Electric Sheep?,” by the late Philip K. Dick, shied away from this subject because it has sticky, neo-Fascist aspects. But this underlying idea is the only promising one in the movie, and it has a strong visual base: when a manufactured person looks just like a person born of woman—when even the eyes don’t tell you which is which—how do you define the difference?