My favourite version of a delusion is the one where someone starts out with a "definition" of God, then proceeds to show how their "definition" means God doesn't exist. An alternative delusion is where someone proceeds instead to show how their "definition" means God might exist. But all they can really show is that they've managed to invent a "definition", and that's all they have. The definition may correspond to something they can read in a book, but that doesn't give it any authority. The only true authority is personal experience, and there is no requirement that you convey in words what you experience. Believing that there is such a requirement is consistent with the delusion that a definition exists.