Can someone explain this quote from "Fahrenheit 451" for me?“There was a silly damn bird called a phoenix back before Christ, every few hundred...

In this quote, Granger, an "outsider" that Montag meets on the tracks, is explaining a legendary story about a bird called the Phoenix.  And, the story is as Granger tells it--there is a bird, who represents society, who builds up a pyre of wood and sets himself on fire.  This symbolizes Montag's society, and how they make mistake after mistake after mistake.  Pretty soon, there is a huge pile of mistakes, just like there is a huge pile of wood in the analogy.  Then, the bird goes too far, and ends up burning itself to death.  This represents Montag's society and how they got to the tipping point, and finally, all of their wars ended up wiping everyone out.  Most of their society is destroyed.  Granger then tells the story of the Phoenix, and how in that tale, the Phoenix just kept making the same mistakes, and so it ended up burning itself over and over again.

Granger doesn't want to end up like the Phoenix.  He doesn't want his world to just repeat its own destruction over and over again.  Instead, he wants to rebuild his society, but not make the same mistakes.  He wants to build his society in such a way that they don't end up destroying themselves again.  He wants to learn from the mistakes of the past so that they don't repeat them again.  It's a good idea, one that is hard to implement in the world--it would be ideal if it was though.  Montag, Granger and the others decide to go back and rebuild again, but to remember what they have learned, and to not make the mistakes that got them destroyed.  I hope that helped; good luck!