Each of the five main characters in The Heart Is a Lonely Hunter strives to break out of his or her isolated existence. The reasons each character is isolated are very different: the deaf-mute John Singer cannot communicate with most of the world because he cannot speak; Mick Kelly cannot communicate with anyone in her family because they do not share her intelligence and ambition; Biff Brannon is left alone when his wife dies; Dr. Copeland is alienated from his family and from other black people because of his education and viewpoints; Jake Blount is alone is his radical social viewpoints and in the fact that he is a newcomer in town.
The isolation from which each character suffers is a combination of personal and environmental factors. However, all of the characters feel profoundly alone in some sense or another, and all of them desperately need to communicate their feelings with somebody who understands them. All five, with the exception of Biff, confide in Singer the things that make them spiritually lonesome. Though it is never made clear, the only reason Biff does not discuss his personal conflicts with Singer is most likely because Biff himself is unable to articulate these personal conflicts. Regardless, Biff still finds Singer's presence comforting. After talking to Singer, the characters almost always feel soothed.
McCullers also uses the novel to explore the idea that all people feel a need to create some sort of guiding principle or god. However, whatever each person conceives of in this godlike role is merely his or her own fantasy; it has no basis in reality, just as those who believe in God have no proof that He actually exists. Singer becomes a pseudo-religious figure for the main characters of the novel; they believe he has infinite and unending wisdom about many things, and they turn to him in times of trouble, constantly asking him to help them achieve their goals and assuage their fears and doubts.
Each character creates a different god in Singer. For Mick, Singer is a man who feels as she does about music and whom she can ask very personal questions—things she has never said to anyone before. For Dr. Copeland, Singer is an the only enlightened white man he has ever met, the only one who understands the Doctor's burning passion to achieve justice for black people in the world. For Blount, Singer is a man who shares his deep concern about the importance of socialist revolution and the eradication of capitalism. For Biff, Singer is, like Biff himself, a quiet and astute observer of the human condition who ponders many things in great depth.
In reality, however, Singer is none of these things; he is merely an ordinary, intelligent man who only wants to be with his friend Antonapoulos. Singer cannot understand why all these other people come to him for advice on topics with which he has no expertise or even familiarity. It is ironic that Singer—a character the others blindly make out to be a sort of god—is just as prone to the same blind faith, which we see in his love for Antonapoulos. Singer believes that Antonapoulos is a wise, kindhearted person, and he worships his friend unremittingly. Meanwhile, it is clear to us that all the evidence suggests Antonapoulos is actually coarse, selfish, and lazy. In the end, we see that all the major characters are deluding themselves by believing only what they wish about John Singer. Nonetheless, the very fact that they believe it gives them peace.
Heroism surfaces most overtly in the novel in the characters of John Singer and of Mick, the least self-absorbed of the major characters and seemingly the only ones capable of feeling genuine, unselfish love for another person. The love Singer feels for Antonapoulos demonstrates the altruism of Singer's nature: he is capable of loving someone completely without receiving any true reciprocation whatsoever. Mick also shows herself to be capable of loving someone for reasons that are not at all self-interested: she feels a deeply affectionate love for her younger brother Bubber, and she continues to feel this way even when he distances himself from her.
By the end of the novel, Mick emerges as the most heroic character when she gives up school to take on a job to help support her family. She is determined not to give up on her dreams; indeed, she is the only character who does not let Singer's death negatively affect the course her life takes. After Singer dies, Dr. Copeland's health fails and he is taken to his father-in-law's farm; Blount leaves town; Biff remains in the same monotonous existence. Mick is the only one of the major characters who maintains positive plans for the future: she is firmly resolved to continue saving for a piano, despite the fact that it will take many hours at Woolworth's before she can afford one. For Mick, there is a light at the end of the tunnel that no other character—not even Singer—sees.
Both Singer and Blount experience dreams that either are indicative of important aspects of their personalities or support some greater theme in the novel as a whole. Singer dreams that he sees Antonapoulos at the top of a flight of stairs, kneeling and holding something up in his hand. Singer is kneeling behind Antonapoulos, while Mick, Biff, Jake, and Dr. Copeland are all kneeling behind Singer. This worshipful image perfectly depicts the way that the characters feel in the story: Singer worships Antonapoulos, whereas the other four characters worship Singer. The dream represents the dynamic of the relationships in the novel as a whole.
Jake has a nightmare at the end of the book that he has had several times before. He dreams that he is in a crowd and that he is carrying a covered basket. He feels anxious because he does not know to whom to give the basket. This dream demonstrates Blount's desire to find kindred spirits who also believe in socialism, so that he can give his "basket" of beliefs to them. In the dream, Blount has been carrying the burdensome basket for a long time; in life, his socialist beliefs have burdened him for a long time as well, as there are few people with whom he can share them to relieve his thoughts.
Singer is a symbol of hope throughout the entire narrative: he embodies Mick's hopes that someday she will travel and become a famous musician, he embodies Biff's hope that he will someday find enlightenment, he embodies Dr. Copeland's hope that someday the black race will have justice, and he embodies Jake's hope that soon workers in America will understand that they are oppressed and will fight for their rights. Each character projects these qualities onto Singer, who comes to stand for all that the characters believe in their own minds. This blank-slate quality to Singer is the reason the others believe in him as they would a god: he cannot directly respond to their pleas, but the mere fact that they believe in him enough to confide in him in the first place affords them at least a small measure of peace.
Mick's attempt at a makeshift violin—a clumsy object constructed of an old ukulele and strings from various instruments—is a clear symbol for her thwarted musical ambitions. Mick wants a piano, a radio, and music lessons more than anything else, but she is mature enough to realize that her family's poverty makes these dreams impossible at the moment. On the whole, Mick is constrained by her environment: she is an ambitious, intellectual young girl in a household and a town where there are few people with whom she has anything in common. Her patchwork violin is a poignant symbol of her loneliness, frustration, and sense of futility in the face of these environmental constraints.