The narrator compares two modes of life or of novelistic subject matter. The first could be related to the everyday dwellings, washed out by a flood, to be seen on the banks of the river Rhone that speak to a past "narrow, ugly, grovelling existence." The second could be related to the castle ruins on the river Rhine. The second consists of lives from the past that are colorful, sublime, and grandiose—a time of beautiful good and extreme evil.
The reader might imagine the story of the Dodsons and Tullivers to belong to the first mode of life, "irradiated by no sublime principles, no romantic visions, no active, self-renouncing faith." The "oppressive narrowness" felt in the tale of the Dodsons and Tullivers may be tedious to encounter, but, "it is necessary that we should feel it if we care to understand how it acted on the lives of Tom and Maggie." The religious or moral ideas of the Dodsons have always been prosaic. They are Protestants but truly revere what is "customary and respectable"; they do not have a striking sense of spirituality. The Dodsons are exceptional only in their conviction that "the right thing must always be done towards kindred." Thus, the Dodsons will never turn their backs on unfortunate kin, though they will be hard on them in their speech.
The Tullivers, by contrast, are not as self-serving as a family but rather show "elements of generous imprudence, warm affection, and hot-tempered rashness." The Tullivers are even less big on religion, valuing common sense instead.
The initial trauma and accompanying adrenaline of the family downfall having worn off, the Tulliver household has become morose and monotonous, with few visitors. Mrs. Tulliver wanders around the house, bewildered at their loss. Maggie begins to feel tenderly toward her mother, who has become pitiful. Mrs. Tulliver, hopeless for herself, has begun to rest some hopes on Maggie, and dotes on her slightly by brushing her hair.
Mr. Tulliver is not his old self. Instead, he is singleminded in his attempt to pay his debts. He has turned into a miser, keeping a rigid hold on the house. He still likes Maggie to be near him, but this is now more of a need than a desire—there is no love in it.
Maggie feels no love any more from her father, nor from Tom, who is just as singleminded about repaying the debts as his father. Yet the money accumulates slowly, and it may be a very long while until they are all paid.
Maggie sits outside, unable to read, as she is distracted by the rage Mr. Tulliver exhibited yesterday after a visit to Wakem. This time he had beaten a boy from the mill and last time he had beaten his horse. Maggie worries that he might hit her mother some day.
Bob Jakin comes through the gate. He gives Maggie several picture books and several prose books, because he remembered her sadness upon having discovered her books had been sold. Maggie takes the books happily, and she asks Bob questions about Bob's dog Mumps to stall his departure. Bob reveals to Maggie his extra-wide thumb that he uses to cheat his old customers of their full length of cloth. Maggie tells Bob seriously that "that's cheating" and that she doesn't like to hear of it. Bob says sincerely that he wished he hadn't said anything and explains to Maggie that his customers attempt to cheat him as well.
After Bob leaves, Maggie sits upstairs by the window feeling incredibly lonely. She has no friends, and life has "no music for her anymore." She feels that even the other members of her family have tasks to focus on or minds dull enough not to mind, but Maggie seeks to understand why her life has become so sad. Even Tom's schoolbooks, and the acquisition of male knowledge they promise, offer little solace. Inevitably, Maggie ends up feeling selfish about her own sadness by remembering her father's.
Maggie sits down to read one of the books Bob gave her, whose author she vaguely recognizes—Thomas a Kempis. The book has passages marked by a previous owner and a low voice seems to speak the passages to her. The book speaks of renouncing self-love in favor of the tranquility of focusing on the sufferings of others and thinking of heaven instead of earth. Maggie feels she has found the secret that will give her the strength to endure happily through her difficult life. Maggie begins to live her life as deprivation and penance, though she sometimes outdoes herself by putting too much "exaggeration and wilfulness, some pride and impetuosity" into her new practice. For Maggie there is still a hint of the old Maggie, who demands full feeling out of life and love and happiness. In her youthful way, she has missed the point that Thomas a Kempis's writings hold implicit that "renunciation remains sorrow, though a sorrow borne willingly. Maggie was still panting for happiness, and was in ecstasy because she had found the key to it."
In her house, Maggie's new demeanor makes her mother proud and affectionate. Maggie's new grace of manner increases her father's gloom at the future he can't provide her.
Book Fourth contains very little plot action and contains no specific scenes other than Bob Jakin's visit to Maggie when he gives her the books. The Book is a short one and focuses on the tenor of Maggie's inner life as the state of her family affairs continues to be difficult. At the opening of Book Fourth, the dreadful, initial excitement of the bankruptcy and Mr. Tulliver's illness have passed, leaving uneventful sorrow. By the end of the book, Maggie has sought to remedy her sorrow and the lack of intensity in her life by adopting Thomas a Kempis's religious mode of self-abnegation over self-love.
The narrative of Book Fourth begins with a distinction between dull, prosaic existence and colorful, sublime existence. Eliot continues to call attention to the lowly status of her subject matter. In Book Fourth, she underscores the sadly prosaic quality of the Tullivers and their situation by referring descriptively to hierarchies and subject matter outside of the main narrative of The Mill on the Floss. Thus, in the opening of Chapter I, the narrator discusses the more colorful subject matter of fantastic narratives that include "robber barons" and "the wandering minstrel, the soft-lipped princess, the pious recluse." Next to these characters, the ordinariness of the Dodsons and Tullivers is emphasized. In Chapter III, the narrator discusses the upper class, who hardly appear in the novel proper—"good society" with "its claret and its velvet-carpets, its dinner-engagements six weeks deep, its opera and its faery ball-rooms." On the one hand, these glimpses at the characteristics of the upper class or of the subject matter of "exciting" literature are somewhat ironic—Eliot knows that she has made the most of her subject matter and that readers are now fully involved in the story of the Tullivers. These comparisons, however, also serve to emphasize the particular dullness of the Tulliver's existence, thus letting Maggie's intense personality and intelligence stand out within it. The stifling atmosphere of her family's spiritual and actual poverty, combined with the penalty of having been born a girl, seem to drive Maggie to the need for release—release found in the spiritual writings of Thomas a Kempis.
A key word for Book Fourth is "sublime," meaning something majestic or something of high spiritual, moral, or intellectual worth. Book Fourth depicts Maggie as striving for sublimity, even while trying to be humble and self- effacing—she views the writing of Thomas a Kempis as "a sublime height to be reached." Though the narrator remains sympathetic to Maggie, the narrator is also unsparing in her explication of Maggie's youthful mistakes. Maggie's enthusiasm and intensity clash with her efforts to degrade and humble herself. Book Fourth contains many metaphors of things high clashing with things low—for example, Maggie "often strove after too high a flight, and came down with her poor little half-fledged wings dabbled in the mud." Maggie's natural impulse toward the heights of sublimity clashes with Book Fourth's title from Pilgrim's Progress, "The Valley of Humiliation." Book Fourth thus fully outlines the battle of opposing forces within Maggie that was alluded to in the last line of Chapter V, Book Third ("No wonder, when there is this contrast between the outward and the inward, that painful collisions come of it.") and that will dominate the remainder of the novel.