What is the promise given at the end of Ray Bradbury's Fahrenheit 451?
Montag's city is blown up by an atomic bomb at the end of Fahrenheit 451. He meets up with a group of men who have memorized books in an effort to save them for some future time when they will be valued by society. The leader of that group is Granger, and as they are all looking at the aftermath of the leveled city from a safe distance, he remembers the phoenix. Granger explains the myth to Montag as follows:
"There was a silly damn bird called a phoenix back before Christ, every few hundred years he built a pyre and burnt himself up... But every time he burnt himself up he sprang out of the ashes, he got himself born all over again. And it looks like we're doing the same thing, over and over... someday we'll stop making the goddamn funeral pyres and jumping in the middle of them. We pick up a few more people that remember every generation" (163).
Granger teaches Montag that people have been destroying themselves for generations, but there is a hope that one day humanity will get it right. Montag thinks of a passage from Ecclesiastes he has memorized:
"To everything there is a season. Yes. A time to break down, and a time to build up. Yes. A time to keep silence, and a time to speak... And on either side of the river was there a tree of life... And the leaves of the tree were for the healing of the nations" (165).
This passage that Montag remembers and wants to share with the others in the hobo camp promises that after things have broken down, then there is always a time of building up that follows. Also, in time, nations will heal and start all over again. Add this passage from Montag with that of Granger's and the reader is left with some hope that the new civilization that rebuilds will learn from past mistakes and create something better than the last civilization.
The promise is that a new era is about to begin and that humanity is not completely doomed. At the end of the novel, Montag recalls the biblical passage, "To everything there is a season. A time to break down, a time to build up." The time for destruction has ended; the time for rebirth has begun.