According to Wikipedia, the correct psychological term for fear of heights is acrophobia:
Most people experience a degree of natural fear when exposed to heights, known as the fear of falling. . . . Acrophobia sufferers can experience a panic attack in high places and become too agitated to get themselves down safely.
In "Contents of the Dead Man's Pocket," the author plays on our "natural fear when exposed to heights." Tom Benecke is experiencing acrophobia to an extreme degree, and we are experiencing it along with him, since we have been beguiled into climbing out there on the ledge with him in our imaginations.
Some psychiatrists such as C. G. Jung would suggest that there are hidden implications in Jack Finney's story. The fear of heights many people experience in dreams has been attributed to an unconscious fear of moving up in the world socially and financially. In other words, a fear of falling experienced in a dream—or conceivably in creating a work of creative fiction—may represent a fear of success. It might even be suggested that Tom Benecke did not really climb out on that ledge but only dreamt he was doing it. The author intentionally creates a solution to Tom's acrophobic problem which will provide positive truth that he was really trapped outside and really in imminent danger of falling to his death:
He heard the sound, felt the blow, felt himself falling forward, and his hand closed on the living-room curtains, the shards and fragments of glass showering onto the floor. And then, kneeling there on the ledge, an arm thrust into the room up to the shoulder, he began picking away the protruding slivers and great wedges of glass from the window frame, tossing them in onto the rug. And, as he grasped the edges of the empty window frame and climbed into his home, he was grinning in triumph.
The shards and fragments of glass on the living-room floor are evidence that the window was broken from the outside. It was not a dream.
Why should anyone be afraid of success? There are many articles about this fear accessible on the internet. One that appeared in Psychology Today includes this paragraph:
"The fear of success is a very unique issue that arises when you are genuinely creating change and moving forward in your life," says Ti Caine, a hypnotherapist and life coach based in Sherman Oaks, California. "The fear of success is very real because the future is real—we're all heading there—and what we imagine for our future has an enormous influence on us."
A classic novel dealing with the psychological problems experienced by a man who is succeeding impressively in the business world is The Rise of Silas Lapham by William Dean Howells. Lapham is a lower-class entrepreneur who feels uncomfortable in the upper-middle-class social world into which his business success is inexorably drawing him. According to the eNotes Study Guide on the novel,
Silas Lapham, a millionaire paint manufacturer in Boston. He is respected in business circles, but his family is not accepted socially. Garrulous, bourgeois, burly, and brusque, he reflects traits of the self-made man who loves his maker, yet he is compassionate with outsiders and loving to his family. Babbitt-like, he emulates men he has admired for their savoir faire. Bankrupt after a series of business reverses, he gladly leaves the material comforts of Boston to return with his family to the modest living of their earlier days.
Sigmund Freud maintained that creative stories or "made-up" dreams could be interpreted in the same way as real dreams. Jack Finney's short story might be interpreted as the author's unconscious expression of his fear of success as a writer. He was a good writer but never an outstanding success. Henry James writes feelingly about the perils of success for a creative writer in his marvelous short story "The Great Good Place." The middle-aged protagonist, George Dane, has achieved international fame as a writer and finds that it is causing him great stress, frustration, and weariness, along with making it more and more difficult for him to do his writing. He dreams of escaping from the responsibilities and demands of his exposed position to a sanctuary he thinks of as "The Great Good Place" where he can be at peace and regain his own soul. William Butler Yeats seems to be expressing the same fantasy in his poem "Sailing to Byzantium."