"How beautiful these gems are!" said Dorothea, under a new current of feeling, as sudden as the gleam. "It is strange how deeply colours seem to penetrate one, like scent. I suppose that is the reason why gems are used as spiritual emblems in the Revelation of St. John. They look like fragments of heaven. I think that emerald is more beautiful than any of them."In Goethe's Faust, Mephistopheles helps Faust seduce the innocent Gretchen by giving her a casket of jewels, and perhaps that scene is recalled here. Dorothea is revealing the sensual side of her nature, which she keeps repressed under her strong (but, in this case, adaptable) religious principles. In this case, she is able to "justify her delight" in sensual pleasures by presenting it to herself as "mystic religious joy." She adjusts her real, immediate, everyday reactions to conform with an ideal of motivation and conduct.
"And there is a bracelet to match it," said Celia. "We did not notice this at first."
"They are lovely," said Dorothea, slipping the ring and bracelet on her finely-turned finger and wrist, and holding them towards the window on a level with her eyes. All the while her thought was trying to justify her delight in the colours by merging them in her mystic religious joy (35-36).
Throughout Middlemarch, Eliot is interested in exploring the conflict between our ideal and actual motives—between doctrine and actual conduct. She's interested in how we justify our actions to ourselves, how we convince ourselves that our motives and actions are consistent with our deeply held principles. Celia says to herself, after Dorothea accepts the emeralds: "Dorothea is not always consistent" (37). Dorothea, like most of us, want our actions to be consistent with our beliefs, but this often requires some mental adjustment.
Look at Mr. Bulstrode, the evangelical banker. He's the most obvious hypocrite of the novel. Outwardly pious and inflexibly doctrinaire, his true gods are power and money. But of course he doesn't see himself that way, and he is careful to find justifications for his own worldly, or inconsistent actions. "It was not in Mr. Bulstrode's nature to comply directly in consequence of uncomfortable suggestions," Eliot writes. "Before changing course, he always needed to shape his motives and bring them into accordance with his habitual standard" (160).
Rev. Camden Farebrother comes across better than most characters in this respect. "Few men who feel the pressure of small needs," Eliot tells us, "are so nobly resolute not to dress up their inevitably self-interested desires in a pretext of better motives" (207). He is, in other words, the antithesis of the hypocritical and self-justifying Bulstrode. He is candid and sympathetic, and conspicuously lacking in doctrine—which is why the evangelical Mr. Bulstrode wants to oust him as the chaplain of the local hospital.
The dilemma for Dr. Lydgate is whether to side with Bulstrode, and vote to oust Farebrother, or side with his friend and incur Bulstrode's dangerous enmity. Eliot shows Lydgate arguing with himself, attempting to convince himself that he has the proper motives for undertaking a self-interested course of action (siding with Bulstrode). When Lydgate finally casts his vote, we see him acting out of small pique and pride, reacting defensively to the comment of another hospital director, grasping at a justification for his self-interested action out of the thin air of circumstance.
Here's Angela Gheorghiu singing "The Jewel Song" ("Oh Dieu! que de bijoux") from Gounod's Faust.