Anthony Doerr chooses this quote because it describes Saint-Malo as a jewel and wants his readers to connect the word 'jewel' to the Sea of Flames diamond.  Philip Beck describes the 182 buildings left standing as if the reason they survived was because of some sort of miracle. And what do we know that makes miracles and gives eternal life? The Sea of Flames. In August 1944, the Americans came to drop bombs into Saint-Malo and we know that after the bombing, Etienne's house comes out unscathed since Marie and the Sea of Flames was in it. It's like this quote was made for the book. I wouldn't be surprised if Doerr based his entire book off this quote.