Technically, it's not an epigraph, but we're going to talk about it as if it were, because it sets the tone for the entire novel. It can be summed up in one word: ANÁΓKH. That's pronounced "an-ang-kay," and it's the Greek word for "fate."
Why Greek, you ask? Aren't these people supposed to be French? Well, classical Greek has a lot of associations with tragedy. In fact, our idea of fate as an inescapable destiny pretty much comes from the Greeks (people like Sophocles, Euripides, and Aeschylus), so it's actually fitting.
But why this particular word? Well, after reading the novel, we can see how Frollo takes the idea of fate and totally runs with it: he sees it as something that propels all of the characters toward an inescapable ending. In the preface, Hugo basically tells us that he wanted to imagine the human story that led to someone to write "fate" all over that on a wall in Notre-Dame. So, he concocted a story about fate and a cathedral.
This brings us to the other important idea that the preface lays out: time. The fact is, the real story behind this piece of graffiti is lost, and it's as though the person who wrote it never existed at all. It's miraculous that even this little fragment of that person survives, and as the author notes, it soon gets covered up during "renovations."
But when time inevitably destroys everything, how do you make anything that lasts? Well, in the author's view, you've got two options:
- You can build a cathedral.
- You can write a novel.
So Hugo opts for Secret Option #3: he writes a novel about a cathedral. And his novel is going to stand as its own permanent monument to this little piece of history.