Brook is a quite simple man.
He thinks, that no matter, where you live, no matter, who you are - matters only lighting, which you should give to two worlds: your inner and rest outer.
He is like an ascetic man, who was sitting long in cave and thinking about the eternal, trying to record all the results on paper. In this way, songs were created. And only a small part of them, like a tip of the iceberg, is available now for a few listeners.