A boy, asleep in the country, is awakened by a strong light outside his window and some strange rustlings in the house. A few feet from his bed, a toy monkey claps its cymbals together—like a stick banging the floor three times in a French theatre, announcing the beginning of a show—and tanks and police cars spin and race around the room. The boy, who has a snub nose and wondering hazel eyes, is not at all afraid. A little later, the house is invaded again, this time not so gently: a Hoover suddenly sweeps across the floor, like a column of Roman soldiers, terrifying the boy’s mother. Out in the street, while light pours down from above, a row of mailboxes rattles furiously, as if under siege from a tornado.

The first hour or so of Steven Spielberg’s “Close Encounters of the Third Kind”—a movie that opened forty years ago—is unparalleled in its combination of scary and funny ideas. In Muncie, Indiana, something has definitely arrived. The aliens extend a galvanizing finger, reaching out not like the Sistine God to a naked and powerful Adam but to a boy, to toys, and to appliances. The American consumer world is thrilled into electric activity, the rubbish scintillated and redeemed. In Spielberg’s movies, transcendent or threatening forces enter ordinary existence, where, despite them, children play and couples quarrel, make up, and split. Life goes on. The people don’t know, so to speak, that they are part of a movie with a fantastic premise: they go to the beach oblivious of the shark; they tidy up the kitchen without noticing the alien in the house. By nature, most of us are busy with small tasks and immediate pleasures; we are self-interested and literal-minded. Yet the boy in “Close Encounters” stands before an open door, and the reddish-gold light beyond beckons him to some adventure he couldn’t possibly have had before.

At the start of “Great Expectations,” Young Pip is terrified by the convict Magwitch rising up in a graveyard and threatening to eat his liver. Spielberg has created, with skill equal to Dickens’s, the strangeness felt by an innocent—the bewildering oddity, the physical enthrallments and terror of something entirely unprecedented. He captures the experience sensationally (in both senses of the word), with all the immersive physical violence that movies are capable of, and also as an abrupt change in awareness. In the famous scene near the beginning of “Saving Private Ryan” (1998), set at Omaha Beach on D Day, the bow ramp of the lead landing craft falls open and the soldiers in front immediately get shot; the rest struggle to get onto the beach, their vision blurred by fear, their hearing dulled by exploding shells. Janusz Kaminski, the cinematographer, works with a handheld camera that thrashes in the water. It is one of the great, tragic sequences in the movies, an experience as bizarre and dislocating as it is deadly.

Steven Spielberg is the most popular moviemaker who has ever lived, yet he has made many people uneasy, even resentful. Some have found him glib, his sense of action larger than life, his frame too busy, his temperament a jarring combination of violence and suburban sunniness. He can be tiresomely old-fashioned. In the spoofing, neocolonial “Indiana Jones” films, the turbaned Arabs and Indians, gesticulating and shouting, bite the dust like braves in an old Western. When compared with his ambitious contemporaries, he doesn’t seem like an artist—he’s not self-punishing and dark, like Martin Scorsese; or mischievous, even malevolent, like Brian De Palma; or complicated, elusive, and bitter, like Robert Altman. He hardly touches the current world of work, identity, and play—his imagination is set either in the past or in the future. Such moods as alienation and melancholia have no place in his films. He goes right down the center of common emotions, often with jolting force. He is positive, external, and patriotic, a public filmmaker.