One example of nobility, or being noble, can be seen in Bradbury's Fahrenheit 451, in the character of Montag.
"Noble" is defined as...
...of an exalted moral or mental character or excellence; principled.
Montag's nobility emerges in the first part, entitled "The Hearth and the Salamander," when the firehouse receives a call to burn down "11 No. Elm, City." When they arrive, they enter...
...swinging silver hatchets at doors that were, after all, unlocked...
They also begin to throw books out of the attic onto the ground and soak them with kerosene. In this instance, Montag notes that in the past, the police always arrived beforehand, subdued the homeowner, and removed him or her so the burning was nothing personal. Montag thinks:
Always before it had been like snuffing a candle.
In this instance, however (and it has a profound effect on Montag), the owner of the house is there, rebuking them with her attitude—her defiance. On previous jobs, Montag had been a dutiful fireman, supporting the government in the burning—
You weren't hurting anyone, you were hurting things!
But this is the first time he sees someone—figuratively and literally—attached to those books, to the house. And this woman is prepared to make the ultimate sacrifice, changing how Montag looks at himself, his career, the government, and books forever. He tries to save the woman.
"Come on, woman!"
The woman knelt among the books, touching the drenched leather and cardboard, reading the gilt titles with her fingers while her eyes accused Montag...
"The whole house is going up," said Beatty.
The men...glanced back at Montag, who stood hear the woman.
"You're not leaving her here?" he protested.
Beatty has no interest in saving the woman. But Montag reaches out to her, pleading with her to leave with him.
"You can come with me."
"No," she said. "Thank you anyway."
Though Montag continues to urge her to leave, while Beatty starts his countdown to torching the place, the woman quietly tells Montag:
I want to stay here.
You can stop counting...
To their horror, especially Montag's, she opens her hand, which contains a single, "ordinary kitchen match." She now urges Montag to go, while the fumes of kerosene rise up around her. As Beatty makes a motion to start his flamethrower, she stares at them with contempt and ignites the match, setting herself and the house on fire!
Montag's character changes when he becomes drawn to the books himself, no longer seeing them as kindling for some enormous bonfire or "spectacle." There is a nobility in how Montag chooses to break with the laws of society—to stop acting like a sheep without a brain. When they burn "11 No. Elm," a book falls into Montag hand, which Bradbury personifies...
A book lit, almost obediently, like a white pigeon, in his hands, wings fluttering. In the dim, wavering light, a page hung open and it was like a snowy feather, the words delicately painted thereon...He dropped the book. Immediately, another fell into his arms.
This book he grabs almost against his will, his hand "closing like a mouth" around it, thrusting it hurriedly into his jacket to conceal it. Montag becomes, from this point, more involved in questioning the government and more interested in the power of books. In defying something he believed to be inherently wrong, he shows nobility, even though he knows—and is fearful—that he could be and in fact, eventually will be, caught.