It makes me very sad the way people talk about Bon sometimes because truly the most salient aspect of his character to me is that he believes this. Everything he says, especially everything he says to Rose, like. He believes this. He believes this is true. He believes this is better. He believes this is beautiful. He looks at Rose and sees a woman drowning, just as he was drowning. So much like him. So much like him. How can he not pull her free? How can he leave her to drown?
To me, that's so much more interesting than the thought that he just lies. It's so fucking compelling the thought that he relates to Rosemary, and that Rosemary relates to him in turn. That they see themselves within each other, and that Bon promises her a future where she does not have to live with the agony of her Self. Where she can finally be free of all the causes of her misery.
Part of this is why I'm sort of dissatisfied with interpretations that Bon views Rosemary maternally. I dislike it a lot in how it relates to Rose's character, but this is mostly a Bon Post so I'm talking about Bon. He obviously regards Rose with a lot of reverence, but he also regards himself with a lot of reverence. He Loves himself, Loves what he has become. He approaches Rosemary as an equal---a broken person, like him. An artist, like him. Perhaps, to him, the greatest artist in the world. The one who created Him, the identity which saved him, the identity he now lives for.
He's so desperate to bring her into his world. To help her. Please, please, let me fix you! He asks her, waits for her permission, because he also wants to prove to himself that his ideology is correct. That it's functional. That it really did help him, so it really will help her. We know he had to trick Susan, because Susan couldn't possibly understand. Susan was too connected to her human life to understand the beauty of what he was showing her. Too ignorant to the pain of the world. Too naive. But Rosemary has suffered. She has been broken almost as thoroughly as he was. She is a ghost among the living, beyond herself, merely haunting her own life. When people look at Rose they see the specter of the woman-who-was, not the woman in front of them. But Bon sees her, the broken her, and loves her because he knows her, knows he can help her. Is so desperate to help her. Because if She is Beautiful, if She is Happy, then it really is true that He is Beautiful, that He is Happy.
That's why The Scene is so important:
He needs to hear it. He needs to know it's true. He needs to know it's really possible for people like them to be fixed. But she isn't. She isn't happy. Bon isn't truly happy, either. But they must tell it to themselves, because otherwise, what was this all for? It's not like they have another option, now.