Cycles come up a lot in Fahrenheit 451 – cycles of construction and destruction. Until he breaks free from his life as a fireman, all Montag knows is the latter. His job, his world, his entire life is about violence, death, elimination. Fire is a great example; it’s used only to destroy books, people, and houses.
So it’s a big deal when, towards the end of the novel, Guy finds a fire that is doing something positive. It’s a warming fire, he realizes with awe. It’s giving life, not taking it away. Montag has stumbled onto a big idea here – the constructive/destructive duality – but it’s Granger who fleshes it out in the last few pages. Like all of life, he explains, mankind’s presence on this planet is cyclical. We’ll do this all repeatedly, he says – go through another Dark Age and have to rebuild and flourish all over again. When the city is bombed to the ground, it is with hope that Montag reaches towards it, finally aware of this big cycle and finally accepting it.
Which brings us to the final paragraph of the novel: the tree of life. Guy has been trying for at least fifty pages to remember some passage of the Bible, but it’s not until his world is destroyed that the words come back to him. Makes sense, right? Something is destroyed, but something is created at the same time. More cycles, more duality. It’s appropriate that the passage in question is about the tree of life. As Guy remembers from the text, “To everything there is a season. A time to break down, and a time to build up.” And we see both in the final pages of the novel.