The focus in these letters is mostly on Harpo. Celie talks about all the hard fieldwork that she and Harpo have done since Mr. ________ returned in a stupor from his rendezvous with Shug. Celie is sensitive to the fact that Harpo is nearly as big and strong as his daddy, yet, contradictorily, "weak in will." Her voice is tender as she describes Harpo's sad and thoughtful eyes.
Part of Harpo's sadness, of course, comes from his being in love, but a good part of it comes as a result of his being a black man, toiling until exhausted in the fields. Also, in Letter 17, we learn that Mr. ________ has told Harpo that the nightmarish scandal of his mother's murder hangs over Harpo, and that it makes him "unfit" as a suitor for his girlfriend.
In Harpo's nightmare of his mother, Annie Julia is torn between Harpo and her lover, symbols of responsibility versus desire. Fatally, she chooses to be a responsible mother.
Harpo's response is to cry out against the injustice of his mother's death. His mother was not to blame, and yet everyone in the community did blame her — because she let her desires seek gratification. And at this point, Harpo's cry of injustice reverberates in echoes, recalling all of the injustices that have been mentioned in all of Celie's letters to God — particularly all of the multiple injustices that have stunted Celie's (Harpo's stepmother's) rightful sense of herself.
Celie's selflessness here, thinking only of Harpo, is almost saint-like. She realizes now that she can never replace Annie Julia, Harpo's mother, just as she herself knew so well, long ago, that Fonso's new wife could never replace Celie's own mother.
As a stepmother herself now, Celie knows for a certainty that she doesn't love Mr._______'s children, and yet that realization does not deter her from acting lovingly toward them. This contradiction in not loving but acting lovingly, as well as the many contradictions of justice and injustice that Celie witnesses every day, coalesce finally in Celie's thoughts about the contradictory nature of Harpo's unwed, pregnant girlfriend, Sofia. Sofia, Celie says, is gentle, yet strong — pregnant and unwed, yet not troubled about the fact. To Celie, Sofia's headstrong, contradictory independence is simply one more fact to be reckoned with. But to Harpo and Mr. _______, Sofia's headstrong independence is an alien and frightening omen.