What strikes me most of all about this chapter from this excellent novel is the way that it presents us with a portrait of Dimmesdale, and in particular how the guilt of his hidden sin that burdens him so profoundly and impacts his health is ironically making him successful in his job as a preacher and pastor. This points towards the hypocrisy of Puritain society and the way that those who love Dimmesdale because of his preaching would be the first to condemn him for his sin of fornication and adultery.
In Hawthorne's The Scarlet Letter, in Chapter 11—entitled "The Interior of a Heart"—the theme I find most prevalent is the dichotomy of sin. Sin has the power to destroy but also to transform. Such is the case with Roger Chillingworth. His sin of jealousy has transformed him into a man intent not just on revenge, but in a long-suffering revenge, visited on Rev. Dimmesdale.
Calm, gentle, passionless, as he appeared, there was yet, we fear, a quiet depth of malice hitherto latent, but active now, in this unfortunate old man, which led him to imagine a more intimate revenge than any mortal had ever wreaked upon an enemy.
Chillingworth allows his own disappointments and suffering to turn him into a sinner equal and perhaps even surpassing Dimmesdale, in that Chillingworth is maliciously inclined to harm, where Dimmesdale's sin was never of that kind. (Though theologically, sin is sin, without degrees of "sinfulness.")
While Chillingworth' soul is deteriorating in his state of sinfulness, Dimmesdale, while declining in his physical health, not only becomes more devoted in atoning for his sin, but is inspiring his congregation all the while. This may not be his intent, but the way he lives his life is uplifting to the members of the church. As he becomes more guilt-ridden, he is being purified like gold in a fire. Dimmesdale's torment can be understood by studying his respect for the truth and how he despises a lie:
...by the constitution of his nature, he loved the truth, and loathed the lie, as few men ever did. Therfore, above all things else, he loathed his miserable self!
As "Interior of a Heart" implies, this chapter gives us the chance to look within the hearts of the two men connected to Hester. Chillingworth loses his soul to the sin that eats at him from within. Ironically, the man of the cloth—who knows of his own sin and suffers greatly for it—is closer to God's will in that he recognizes his sin—which Chillingworth does not—and spends long, painful hours in penitence. In deed, from Dimmesdale comes something valuable, even in light of sin.
Sin transforms both men: Chillingworth loses sight of his moral direction, ironically falling off the same ethical platform from where he stood to so harshly judge Dimmesdale's sin. Dimmesdale, on the other hand, perpetually atones for his sin, and turns his life around while more powerfully reaching out to his congregation because of his fall from grace and his remorse.
Hawthorne's theme stated in Chapter XXIV, Conclusion, is
Be true! Be true! Show freely to the world if not your worst, yet some trait whereby the worst may be inferred.
For, secret sin steals the very life from a person; it tortures him and causes the deterioration of the body. In Chapter XI, then, the reader perceives Dimmesdale agonizing under his secret sin and the resulting hidden guilt just as the vindictive Chillingworth "became not a spectator only, but a chief actor, in the minister's interior life." So, he, too, harbors a secret sin--that of violating the human heart. As Chillingworth has told Hester in his interview with her at the prison, "He will be mine!" But, he too, will suffer from the evil he harbors in his heart. In another phrasing of his theme, Hawthorne describes what happens to both Dimmesdale and Chillingworth when he writes,
No man, for any considerable period can wear one face to himself, and another to the multitude, without finally getting bewildered as to which may be true.
Dimmesdale tortures physically his body while he utters a bitter laugh. Chillingworth transforms later into a fiend.
One way that chapter 11 is significant to the theme of The Scarlet Letter has to do with what mankind expects of religion and morality. With Dimmsdale being the representative of both great morality (outwardly) and great sin (inwardly), I think we see the paradox of every man. So much is hidden from society on the inside, within the soul of mankind. Conversely, on the outside, we reveal appearances. The Scarlet Letter is much about appearances and reality. Hester's letter represents her sin as people understand it, but by the end, it represents her angellic features. On the inside throughout the story, we readers experience her reality... a woman who was caught in a real love while trapped in a society that would not accept it. In chapter 11, we see the same in Dimmesdale, he is trapped in the silent torture of knowing his reputation versus his anonymous sin. I love that the common man gets to read about the fallibility of a man of the cloth. It levels the playing field.