Ugh. Guys, we wish that we could tell you that the Marquis de Rollebon symbolized world peace or true love… but our noses would grow five feet long, Pinocchio-style.
The Marquis de Rollebon is a totally obscure historical figure that no one but Antoine seems to care about. The thing is, though, that writing a book about the Marquis is the only thing that keeps Antoine going for most of this book.
As a rich dude, Antoine doesn't need a job to eke out his daily existence. That gives him a lot of free time to think about the meaning of life. He finds that the only way to give his days meaning is to engage in some sort of project, and since no one has bothered to write a book about the Marquis, he makes for a perfect subject for Antoine's book.
Unfortunately, Antoine can't help but feel at times that the,
M. de Rollebon bores me to tears. (6.15)
Worse still, he realizes that no matter how much he studies the guy, he'll never succeed in bringing him back to life… since dead people no longer exist and it's pointless to try and bring them back to life in a book.
Ultimately, Antoine decides to abandon his project on the Marquis. His final decision is that:
My past is dead. The Marquis de Rollebon is dead. (31.2)
In other words, he can no longer fool himself into thinking that his history project actually makes his life meaningful. The Marquis de Rollebon doesn't exist any more.
Death is final, and the world doesn't care about people who are dead. There's no point in trying to leave behind a legacy, because as far as Antoine is concerned, you either exist or you don't.