Pym is by no means unprecedented. We may place it in a continuum of Poe's writings; we may also place it in a continuum of writings concerned with the fascination of the unknown.
The first of the texts gathered here is a tale of a voyage to the interior of the earth. Symzonia has been hailed as the first science fiction in print. The name of its author, Adam Seaborn, suggests a first-man quality, something often cultivated by explorers. The fact that this imaginative name was never connected to an actual person led to the conclusion that "Adam Seaborn" was the pseudonym of John Cleves Symmes, author of the Theory of Concentric Spheres and proponent of a hollow earth.
No direct evidence links Poe to Symmes or his theories (Poe did write positive reviews of Symmes' protege Jeremiah N. Reynolds in the Southern Literary Messenger). Symmes and his ideas were such a part of popular culture in the 1820s and 30s that it is entirely possible, and probable, that Poe at least got wind of them. It does not seem too much of a stretch to think that had Poe but heard the utterance, "hollow earth," his imagination would have lighted on these words and appropriated them for its own use.
The journey enacted in Symzonia, the journey to the interior of the earth, can be construed as a journey of anti-discovery. It is a journey to discover an emptiness. As does all Utopian fiction, the journey of Symzonia contains a tension. A Utopia is both a "good place" and "no place;" the journey to the interior of the earth is the ultimate journey and the impossible journey. It finds, in those imaginatively inclined, a correlative in a journey into the mind itself, whose outcome will be the unveiling of the deepest secret of humanity.
The grip that the notion of a hollow earth might have had on Poe has to do with a fear that the human mind, rather than containing ultimate knowledge, is, at its very core, empty. The fear of nothingness, of absence, figures greatly in American literature.
Poe's repeated portrayals in his stories of life in death and death in life represent his grappling with the prospect of man's abandonment by his inner being. This is a theme not broached by Seaborn or Symmes. Poe's process was very much one of latching on to a popular idea and transforming it into a mental experience all his own.
The predilection towards appropriation is apparent in the pairing of Pym and Benjamin Morrell's Narrative. Poe stole entire sections of Morrell's Narrative, though it also seems that he sometimes stole, then deliberately deviated to further his own design.
Much as Poe is prey to a robber imagination, he is also a constant seeker of control. His stories are tightly wound capsules in which, ideally, every sentence leads to the outcome. His narrators rationalize their actions to a point that transcends rationality. Personally, Poe prided himself on an ability to solve any cipher sent him. The sense that pervades Pym is of the quest for solution of the ultimate cipher, of the cipher beyond any conceived. For this quest there are pretexts; for its solution, none.