The unreliable and limited nature of sensation is one of the themes that runs through the story and is often highly symbolic. When the reader first encounters Whitney and Rainsford, they are sailing through a darkness as thick as "velvet." The island lies in that darkness, and as Whitney notes, while Rainsford has "good eyes," there is still no possibility that he would be able to see it. The two are, effectively, sailing blind. Whitney, however, does supply Rainsford with information about the island, should he care to accept it. It is Rainsford's own fault that he chooses not to listen to these warnings—to close his ears against them—and thus fall into trouble. Even when he first sees Zaroff's house, he does not believe the evidence of his own eyes, thinking it a "mirage." In Rainsford’s case, his limited sensations are symbolic of his relative powerlessness and ignorance.

This theme recurs in the person of Zaroff's servant, Ivan. Ivan is a "gigantic" man of enormous physical strength, but Zaroff could have recruited such a man anywhere. At the end of the story, after Ivan has died, Zaroff worries about the possibility of replacing him. One can infer that Zaroff's greater concern is that another servant would not be as "mute" as Ivan, who can neither hear nor speak. Ivan responds to Zaroff's instructions unquestioningly, and what he actually feels about the situation, he cannot express, because he is unable to speak. Like a trained animal, he is subservient to Zaroff, mutely obedient. And his thoughts, whatever they are, remain beyond the understanding of others.