Due to the invisible facts, the traces are precious. The ancient texts are also traces. More generally, the books are the precious traces of the work produced by the invisible facts. In other words, they are the observables. The traces are the proof that something exists. This is the crucial point of the miracles. Because miracles are traces of the invisible facts that characterize someone. With the traces, you don’t need to believe, you just see. The traces, as visible parts of the invisible, are more obvious to everyone. That’s why they are needed at the lowest level of knowledge because they constitute objects of the subject.