When we first meet Faber, why is he so critical of himself and pessimistic about the world? Why is he then willing to become Montag's mentor?
Faber regrets that he didn't speak up and try to stop the world from changing. He feels that he was a coward. When the time came to speak up, he chose not to. By the time Faber felt like he needed to speak up and change things, it was too late—others had either been silenced or chose to stay silent.
He explains to Montag:
"Mr. Montag, you are looking at a coward. I saw the way things were going, a long time back. I said nothing. I'm one of the innocents who could have spoken up and out when no one would listen to the 'guilty,' but I did not speak and thus became guilty myself. And when finally they set the structure to burn the books, using the firemen, I grunted a few times and subsided, for there were no others grunting or yelling with me, by then. Now, it's too late." Faber closed the Bible.
Faber, a retired English teacher, feels that he let his opportunity to effect change pass and that because of him and people like him, the world is worse. He believes it will end in war.
When Montag asks for Faber's help, he essentially tells Montag that it is hopeless to try to change things now, saying, "Why waste your final hours racing about your cage denying you're a squirrel?" He tells him to go home.
Montag asks whether Faber would like to own his copy of the Bible; Faber says yes. Montag begins to tear pages out of the Bible and crumple them in front of Faber. Faber begs him to stop; Montag reminds him that he can burn anything because he is a fireman. Ray Bradbury writes:
"The book. Don't tear it any more." Faber sank into a chair, his face very white, his mouth trembling. "Don't make me feel any more tired. What do you want?"
"I need you to teach me."
By threatening something Faber deeply desires, Montag gains his help.
Faber is critical of himself because he feels guilty for having said nothing when this society began to change. He felt that there was a time when he had an opportunity to stop things from happening, from books being destroyed because he was a great mind, but he said nothing for the very reason the society changed- not to upset anyone or the balance of things. In keeping silent he feels he contributed to the almost irreversible changes that have taken place.
He is not entirely willing to become Montag's mentor, in fact he refuses to do so at first, but then Montag threatens him into it. Montag has brought a copy of the Bible and Faber is fascinated and overwhelmed with its presence. After refusing to teach Montag, Montag begins to burn pages of the sacred book before Faber's very eyes until he is finally forced to agree so the burning of this rare treat can cease.