A key theme in this short story is isolation caused by a lack of connection between people in contemporary society. Dickens was writing in a new industrial world, wherein "great works" such as the railway were still recently implemented marvels, born out of technological advancements which were changing the world. Dickens often wrote about the changes, often for the worse, wrought upon society by the rise of the factories and the shift in attitudes to technology. In this story, the signal-Man, an intelligent and educated person with a quick intellectual curiosity, works a job on the railway, which results in his living in isolation in a box. It is evident that he rarely receives visitors. This is not a natural state for a man to be living in. The tasks he performs, too, seem to amount almost to his being a servant of the railway itself, rather than the people who use it. He is to "change that signal, trim these lights, turn this iron handle"—his entire purpose is to keep the railway functioning. He does not have cause to speak to the passengers, or even the drivers, on the railway itself. His life has been changed by these technological advances, but he does not benefit from them.
Meanwhile, the narrator himself is also, seemingly, a rather isolated person. He has "been shut up within narrow limits all his life" and is "not happy in opening any conversation." Something compels him to go down and speak to the signal-man, but it is not his personality or a desire for his company, as such. Rather, the narrator is driven out of his solitude by a sense of intrigue; as time goes on, he notes that the signal-man's anxiety about his duties seems to be intense. This is explained, of course, through the signal-man's stories about the apparitions he has seen on the railway, but there is no easy story to these ghosts. Indeed, what upsets and unsettles the narrator most at the end of the story is the "coincidence" of hearing from the engine driver "not only the words which the unfortunate Signalman had repeated to me as haunting him, but also the words which I myself—not he—had attached, and that only in my own mind, to the gesticulation he had imitated." The narrator cannot understand why this strange connection should have been drawn between the three people who do not know each other at all, nor what hand the supernatural has to play in it. It is almost as if the supernatural is a manifestation, in this story, of the wider social anxiety that has arisen in this post-industrial world, and which in the end has caused the death of the railway's loyal...
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