While the major characters serve well to develop the theme of sin and guilt, Hawthorne's lack of dialogue and failure to create ones that reflect the individuality of his characters blurs their development. Instead, they serve more as voices for Hawthorne himself as narrator,becoming more allegorical and symbolic than real.

Hester Prynne 

Not a Puritan, Hester falls under the stringent Puritan laws and is publicly humiliated and labeled as an adulterer, forced to wear a scarlet A upon her bosom. Accepting her guilt, she begs the governor and Reverend Wilson to allow her to keep Pearl as a reminder of this offense and as a preventative against further sin. That Pearl acts as a redemptive source more than the scarlet letter is evidenced when Hester departs and she encounters Mistress Hibbins who invites her to accompany her into the forest to meet with the Black Man. Hester replies,

"I must tarry at home, and keep watch over my little Pearl. Had they taken her from me, I would willingly have gone...and signed my name in the Black Man's book...with mine own blood!"

Ostracized from the community, Hester's letter becomes "the symbol of her calling" as she turns to works of charity, attending the sick and dying. Her unconcern for herself and deep love for the Reverend Arthur Dimmesdale are demonstrated in her overtures to get him to leave the country and in her pleading with Roger Chillingworth to relinquish his hold upon the minister's spirit.

Hester's punishment does little to reform her spiritually; in Chapter XIII, "Another View of Hester," the effect of the scarlet letter is negatively physical, altering her once radiant beauty, and mind altering. Indeed, "[T]he scarlet letter had not done its office" of making Hester conform to Puritanism. Rather, she has "assumed a freedom of speculation," a crime "deadlier than that stigmatized by the scarlet letter." Hester's envisions the future requiring a veritable position of independence for women. Unrepentant of her sin, as well, Hester wonders if she and Pearl might be better off dead.

Although she is able to find some redemption in good deeds and her loving overtures to save Dimmesdale, so terribly affected is Hester by the Puritan gloom and the stigma attached to her that she essentially loses her identity to the scarlet letter and must return from England to replace the worn letter upon her breast.

Pearl

As "the scarlet letter endowed with life" Pearl certainly acts as a symbol of Hester's and Dimmesdale's sin. Described as an "elf" and "imp" and "sprite" who teases and tortures Pearl reminds Dimmesdale of his need to admit his sin. When he finally does, it is then that Pearl attains humanity.

Roger Chillingworth

The greatest sinner, Chillingworth sins against Nature by marrying Hester who does not love him; then he "violates the sanctity of the human heart" insidiously playing God in his revenge against Hester and Dimmesdale.  His ugliness of soul is symbolically reflected in his development into a fiend, a fiend that eventually withers and dies, although he leaves his fortune to Pearl.

Arthur Dimmesdale

A passionate, sensitive and weak man, Dimmesdale has the tragic flaw of being unable to admit his sin and repent. He rationalizes that he can yet serve God if he keeps his sin secret; otherwise, he will be condemned by Puritan law which allows no redemption by good deeds. He is the central character because he struggles with secret sin and finally changes in his confession.

In Hawthorne's The Scarlet Letter, there are four characters that develop and change throughout the novel.

Hester Prynne is found guilty of adultery, though she never names the man with whom she committed adultery—who fathered her daughter, Pearl. When Hester is first found to be guilty, she wears the "A" on her dress and quietly suffers being ostracized from the circle of her Puritan community. At one point, when she meets Dimmesdale in the woods, she removes the scarlet letter feeling the need to be free of it. However, by the end of the story—years after she has taken Pearl away—Hester returns. She has become accustomed to the letter. She is accepted once again within the community, known for her charitable works. The "A," which was once a punishment almost too heavy to bear, has become a part of who she is, and she has made peace with it.

She had returned, therefore, and resumed,—of her own free will...—resumed the symbol of which we have related so dark a tale. Never did it quit her bosom.

It is noted that after so long, the letter was no longer a stigma. She was no longer scorned or criticized. Hester had led such a penitent and unselfish life in the community, that the "A" eventually inspired "awe" and "reverence." People admired her, and many women came to her to share their sorrows and look for guidance. Hester bore them no ill-will.

Pearl is described in critiques of the novel as a one-dimensional character that calls for penitent behavior from her mother (when she refuses to let her take off the "A" in the woods), and chastises Dimmesdale for not exposing his part in the affair with Hester. In these situations, Pearl...

...becomes the figure of authority.

Old beyond her years, Pearl does not take on the true nature of a loving, fully developed character until Dimmesdale exposes his sins of adultery and hypocrisy on the scaffold.

Pearl kissed [Dimmesdale's] lips. A spell was broken. The great scene of grief...had developed all her sympathies; and as her tears fell upon her father's cheek, they were a pledge that she would grow up amid joy and sorrow...but be a woman in it.

Roger Chillingworth, who is Hester's husband, pretending to be a physician for most of the novel (acting as a stranger to Hester) has done everything possible to destroy Dimmesdale, not only physically, but also by poisoning the minister's heart and mind out of revenge. When Dimmesdale confesses, old Chillingworth's twisted satisfaction in tormenting Dimmesdale ends, for the truth is out. Dimmesdale condemns Chillingworth also as a sinner, as he lies dying. After the preacher's death, the old man changes:

All his strength and energy—all his vital and intellectual force—seemed at once to desert him...he withered up, shrivelled away, and almost vanished from mortal sight.

Once wielding enough power to break the gentle but weak-spirited Dimmesdale, Chillingworth becomes a victim of his own poisonous nature.

...there was no more Devil's work on earth for him to do...

...and Roger is lost. He dies within a year of Dimmesdale's passing.

Dimmesdale has been a man too weak to admit to his sins; he hypocritically chastised others from the pulpit for their sins, even as he suffered torment and guilt. On the night of his death, he finds grace enough to publically acknowledge his sins and pray for forgiveness, finally assuming responsibility for his actions—joining Hester and Pearl on the scaffold—redeemed and at peace.