In Book 1, Chapter 1, Amory meets Monsignor Darcy for the first time. The two hit it off immediately, and Fitzgerald makes a clever allusion to describe Monsignor's appearance and cement is appeal to the young Amory.
Monsignor was forty-four then, and bustling—a trifle too stout for symmetry, with hair the color of spun gold and a brilliant, enveloping personality. When he came into a room clad in his full purple regalia from thatch to toe, he resembled a Turner sunset, and attracted both admiration and attention.
In order to illuminate Monsignor Darcy for the reader, Fitzgerald makes an allusion that compares Monsignor's outfit to the legendary paintings of the 19th century English painter, J. M. W. Turner, who frequently depicted sunsets as overwhelming washes of color. Through this invocation of visual art, Fitzgerald tethers Darcy's description to clear visual imagery while also emphasizing the priest's over-the-top, patrician tastes in art and literature. As he does throughout the novel, Fitzgerald's language adopts elitist references of its own in order to keep pace with the characters at hand and to satirize their extreme wealth and pseudo-sophistication.
In Book 1, Chapter 3, Amory has a startling lapse in his cool, calculating demeanor as his sanity appears to waver on a night out with his friends in New York. In the sequence that follows, Fitzgerald uses a host of literary devices—including imagery, metaphor, and simile—to detail Amory's hallucinogenic feeling of horror:
There was a minute while temptation crept over him like a warm wind, and his imagination turned to fire, and he took the glass from Phoebe's hand.
Fitzgerald's language mirrors Amory's feverish state of mind through the use of tactile imagery ("warmth" and "fire"), which appears in both a simile and a metaphor. Amory's sudden feeling of temptation—the urge to indulge after an uncharacteristically sober evening—feels like a "warm wind." And then, as his mind begins to hallucinate, his brain "turns to fire." The incendiary, even violent undertone of this metaphor anticipates the horrifying sequence to come, in which Amory will see a mysterious man who seems to be his deceased friend, Dick Humbird.
Until this point in the novel, Amory has seemed to be unaffected by the sudden death of Humbird in a horrible automobile accident. The intense mood shift that this passage precipitates reflects the intensity of Amory's sudden confrontation with Humbird and, for that matter, with his own unprocessed emotions.
In Book 1, Chapter 3, the illustrious Monsignor Darcy tries to give Amory some much-needed advice. In doing so, he uses a luminous metaphor to put Amory's growing pains in the perspective of the long arc of an entire human life:
[...] and don't worry about losing your "personality," as you persist in calling it; at fifteen you had the radiance of early morning, at twenty you will begin to have the melancholy brilliance of the moon, and when you are my age you will give out, as I do, the genial golden warmth of 4pm.
This is one of many metaphors of age and the process of getting older in This Side of Paradise. Monsignor uses the imagery of changing light to reassure Amory that he is progressing and growing well and that there is much change and growth to come. At this moment in the novel, Amory just wants to be "radiant"—attractive, desirable, and high-class—and doesn't want any of this radiance to fade. Monsignor's metaphor provides some consolation that his radiance will change but won't diminish. What's more, with this use of imagery and metaphor, the text itself seems to glow with the warmth of Monsignor's words and his affection for Amory.
In Book 2, Chapter 5, at the close of This Side of Paradise, Amory finally understands himself after a novel of striving for some unreachable persona. Fitzgerald imbues this triumphant sequence of realization with the imagery of light and glass:
And he could not tell why the struggle was worth while, why he had determined to use to the utmost himself and his heritage from the personalities he had passed...
He stretched out his arms to the crystalline, radiant sky.
"I know myself," he cried, "but that is all."
Fitzgerald encapsulates all the fragility and beauty of Amory's self-knowledge in This Side of Paradise within his description of the sky at the very moment of Amory's inspiration. Using the visual imagery of a shining glass crystal or prism—a symbol of his new clarity—Fitzgerald casts the sky as a gorgeous but delicate object before Amory's eyes: a glowing mirror to Amory's new but nonetheless tenuous grasp on life and its meaning.
This is the moment that Amory becomes a fully realized human being, or, rather, the moment that Amory fully realizes that it is enough in this new modern world to understand oneself—and that it's unnecessary to aspire to anything more. This act of knowing is a delicate, paradoxical, and extremely personal affair. Like a shard of crystal, it is beautiful but extraordinarily fragile.