Sleepwalking
Two of the novel's main characters, including its protagonist and narrator, suffer from somnambulism, or sleepwalking. Both Clithero and Edgar sleepwalk because of emotional duress, and in that condition, they work to achieve their unconscious goals, and vent feelings that they naturally suppress when awake and conscious. So for Brown, sleepwalking allows characters to revel in their darker, less proper impulses. Sleepwalking taps into their deepest desires, fears, and motivations. As Edgar explains it, "the incapacity of sound sleep denotes a mind sorely wounded" (11). It is also an effective way for Brown to avoid painting his characters as complete villains, since they cannot be held entirely responsible for what they do while asleep. Finally, it is worth noting that the second half of the novel (after Edgar wakes up in the pit) dives into Edgar's more violent impulses, as though it were all an aftereffect of having sleepwalked in the first place.
Savagery
Savagery abounds in the novel, but it is not all confined to the Delaware Indians. In fact, although Edgar refers to those warriors as savages, his own character reveals a pronounced savagery as the novel progresses. In his attempt to navigate the wilderness, Edgar feeds on the flesh of raw panther, and murders several Indians, some from vengeance alone. Despite his repeated insistence on disdaining bloodshed, his adeptness with the weapon (and frequent use of it) suggests a deeper impulse towards violence. He seems mildly surprised by his behavior, but the reader can certainly discern a deep-seeded savagery within. Though Brown's novel is not overtly moralistic, the suggestion is that everyone has the capability for savagery, especially in a frontier world that lets self-described 'civilized' people rationalize savage behavior. That the novel is both a critique of a social problem and an exploration of a deeper human characteristic is testament to its oblique nature.
Guilt
Many of the characters in this novel are overcome with guilt. Clithero is the best example. He feels guilty that he killed Arthur Wiatte and that he nearly killed Mrs. Lorimer and Clarice, so much so that he contemplates and attempts suicide by starvation. His debasing and debilitating guilt leads him both to sleepwalk and then into madness. Overall, Brown's suggestion is that guilt implies a disconnect between our conscious, constructed personas and our deep-seeded subconscious desires, which are not always so attractive. In other words, Clithero outwardly loves Mrs. Lorimer but clearly has some complicated subconscious feelings that would suggest murder to him. Seen in this way, Edgar becomes a far more interesting character since his own descent into the subconscious suggests a deep degree of misplaced guilt, whether over his feelings towards Waldegrave, Mary, or his strict Quaker morality. In the end, Brown suggests that misplaced guilt can be a dangerous thing.
The unconscious
Edgar and Clithero may sometimes be awake and conscious in the novel, but they spend just as much time under the spell of their unconscious as they traipse through Solesbury and Norwalk, asleep or transformed by fear/mania/guilt/rage. Clithero's unconscious, teeming with desire for Clarice, anger over his social situation, and fear of Arthur, leads him to murder. When these unconscious desires confront his conscious awareness, he is slowly driven towards suicide and then full madness. Similarly, Edgar must navigate the complicated disconnect between his conscious personality and unconscious desires. On the surface, Edgar seems to be an enlightened and virtuous Quaker, and often espouses values that reflect this background. And yet he clearly harbors unconscious feelings of jealousy, rage, paranoia, and greed. He is able to rationalize many bizarre and grotesque behaviors, which range from breaking into someone's house to eating raw flesh and committing murder. It is notable that Edgar is driven by his unconscious even when awake in the second half of the novel, after he wakes in the pit. Although Brown's work predates Freud's, the novel is a fascinating study of the dark and deep impulses that motivate "civilized" folk.
The frontier
The American frontier in the 1780s and 1790s, when the novel is set, was rife with tension and chaos. The new nation was still in a precarious position, made uneasy by fears of disloyalty and notable xenophobia. For Brown, the frontier is more than a setting; it is a symbol of a people split between high ideals and darker undercurrents of lawless unease. Settlers on the fringes of these newly-created states were subject to Indian raids, while immigrants from different religions and political persuasions were flooding the country. Both of these situations created pronounced distrust of 'the other,' of those people who were not clearly descended from colonial America. The characters of Edgar Huntly are dealing with a severe displacement because of these contradictions. Lawlessness permeates their world, and their psyches gradually become unhinged. The frontier is thus a place that allows the characters to give vent to their frustrations, fears, and desires.
Narrative
All of the themes of disconnectedness - the unconscious, guilt, 'the other,' and more - are reflected as well by the novel's exploration of narrative itself. Edgar begins his letter to Mary by suggesting he will quell his emotions so he can tell her what has happened to him, and yet the act of storytelling itself requires him to delve back into those emotions (rather than quelling them). His narrative becomes a confusing jumble of repetition and doubling. The more Edgar seeks to control his novel, the more it spins out of control. This messiness mirrors the messiness of Edgar's psyche, and emphasizes his unreliability as a narrator. Much in the same way that Brown sees man as attempting to construct an orderly personality that is undercut by a messier unconscious, Edgar struggles with telling his own story.
The other
In this case, 'the other' refers to man's tendency to see people who are different from him as being inferior. The most obvious manifestations of this theme in the novel come with the Indians and immigrants. Both of these groups are viewed as backwards, and are immediately deemed untrustworthy. In a time of immense turmoil and instability, the 'other' was looked at with suspicion; Brown captures that reality in Edgar Huntly. That Edgar becomes much like these people - his own life begins to mirror Clithero's, and he shows himself capable of at least as much savagery as he believes the Indians capable of - provides a suggestion that every man is capable of becoming 'the other,' and that we all have a darker reflection of ourselves within.
The theme has a larger application in this novel in terms of gender. In many ways, women are 'the other' as well. The late 18th century was built on a firm hierarchy of gender and race, with white men occupying the top position. Women were supposed to remain in the home and create an atmosphere of warmth, virtue, and civic responsibility. Brown gives some of his female characters a small degree of autonomy (Mrs. Lorimer and Old Deb, specifically), but they are relegated to their traditional second-class positions by the end of the novel. Any wealth or property that they possessed ends up in the hands of their husband or white settlers, respectively.
