"I can copy things without knowing how they work. Angels have a harder time with the detail work - and they're slower - and they need raw materials, so being a demon is the best deal overall. But I do have to know something about what I'm copying. I can make a book I've never read with title and author, but I can't just guess that there must be a book with such and such an ISBN and produce a copy. Also, I'm pretty sure if I make a phone it will not start out subscribed to Verizon or whatever phone companies are popular these days."