DANIEL MARK EPSTEIN explains in the WSJ review of “The Power of Movies” what happens when we are at the movies.

Seduced, disturbed, beguiled—something strange and compelling happens when we watch a movie: When my daughter was four years old, we took her to see “The Wizard of Oz.” She emerged from the darkness transformed: For the next half-year, we had to set an extra place at the table for the Scarecrow, who had become her constant friend. The girl had gone so deeply into the world of the movie we wondered if she would ever return. Her experience had a certain resonance for me. The first movie I ever saw was “Hans Christian Andersen,” starring the golden-haired Danny Kaye. Since then I have never seriously considered any career other than the writer’s trade. If my first movie had been “High Noon,” would I have wanted to be a gunslinger? Or “The Red Shoes”—would it have made a ballet dancer of me?

Hard to believe, but it is possible. The cinema has strange, seductive, magnificent powers. If you have ever wondered why the movies have such force, attracting crowds in the millions and budgets in nine figures, philosopher Colin McGinn has some answers. At the center of “The Power of Movies” is the “dream theory” of cinema—that movies function like dreams. The idea has been around for about as long as the silver screen, which is probably about as long as people have called Hollywood the dream factory. But in Mr. McGinn’s lively book, the theory at last finds an ample and explicit expression.

First he describes what is peculiar about film-watching and notes that movies are one of the few things that we look into rather than at. Others include “holes, water, windows, mirrors, microscopes, the sky, flames, eyes, and the mind.” I wish he had added books, but let it go for now. Mr. McGinn explains how the experience of each of these helps us to understand what happens to us in a movie theater.

Windows evoke the voyeurism of film-watching, for instance. Mirrors remind us that the framed movie “is a kind of delayed-action mirror, since the events reflected are not occurring at the time of viewing.” Over the centuries, the sky has taught the human eye how to look into things, and “whatever aura of mystery or fascination attaches to the sky…will transfer itself by analogy to the screen.” The stars in the night sky are “the celebrities of the heavens,” and so we have film stars, by analogy. The eye, in Mr. McGinn’s opinion (if not Bette Davis’s), is the greatest subject of cinema, because the eye—the window of the soul—is something like the movie screen. When we look into the screen, he observes, “it is (metaphorically) as if we are looking into a mind.”

Painting, sculpture, theater, ballet—these are all things we look at. But the cinematic image is transparent, even self-effacing. The movie image is a product of “pure light,” Mr. McGinn observes, with no texture and no mass. The pattern of light on a screen produces an image of Orson Welles as Charles Foster Kane. We look through the image of Welles toward Kane, and “our relation to Kane is mediated by our imagination.” Like dreaming, movie-watching is a highly imaginative experience.

Mr. McGinn is building a case that the movie image is perfectly suited to accentuate the immaterial properties of human nature, the mind and soul. “The film image of a person is analogous to this notion of the spiritual or dematerialized body,” he writes. Think of Garbo in “Ninotchka” or Meryl Streep in “Sophie’s Choice” and how these sensual actresses achieve an ethereal clarity in their close-ups.

From this point the dream theory irresistibly unfolds. Mr. McGinn argues that our innate dream mechanism prepares us to understand the fractured, discontinuous space of movies the first time out. I did not have to teach my daughter the montage techniques that transported Dorothy into the Land of Oz. She had known dreams as fractured and emotional as Dorothy’s.

Similarities between dreaming and movie-watching range from the self-evident to the surprising. Because of the power of movies to penetrate our consciousness, Mr. McGinn writes, a film resembles the “emotional seeing” of dreams. Like dreams, movies provide catharsis. Like dreams, they mix fantasy and reality. But what about the fact that in movies, as in dreams, “the minds of others are as transparent as our own”? Here Mr. McGinn has struck gold. I had never before understood how Brando, his rolling eye on the screen, was able to convey to me all that the Godfather was thinking. It is owing to the kinship between dreams and movies: “Both offer us this enhanced psychological presence, this mental foregrounding, this dematerializing of the body…as if minds are shining out at us.”

So a good movie induces a dreamlike state in which our imaginations are stirred and our emotions engaged by other hearts and minds. These, in turn, are made more accessible because the medium where they live resembles that of the mind itself. Our base, instinct-driven self is aroused while the critical, analytic self takes a rest. When we open our minds to Hitchcock’s art, or Spielberg’s, we are giving these artists access to our most private spaces, where our deepest hopes and fears abide. We emerge from the theater yawning and blinking, as if after sleep, and images pursue us—the Scarecrow, the shark in “Jaws,” Charlize Theron.

Mr. McGinn writes briskly, vividly and lucidly. When he trips up, in my view, it is where he has speciously argued a general principle from his own experience. He claims, for example, that there are no dreams without emotion. This is not true for me. He insists that movies are inherently more absorbing than novels and resists the plausibility that we look into the prose surface of a novel as we look into the flat pattern of light on a screen, to see the images and stories beyond. But these lapses we may pardon as the price of admission to the mind of this author and his illuminating book.

Mr. Epstein, a poet and biographer, is the author of “Lincoln and Whitman” (Ballantine, 2004).

The Power of Movies
By Colin McGinn
Pantheon Books, 210 pages, $24