The Spirits' Book
Book Three - Moral Laws
Chapter VI - V. Law of Destruction
756. Will a society of good people one day be purged of sinners and criminals?
“The human race is progressing. Those who are under the power of wrongdoing and who are out of place among good people will gradually disappear, just as defective grains are separated from the good when wheat is threshed. These spirits are reborn into another body and as they acquire more experience, they will arrive at a clearer understanding of good and evil. You have an example of this in the plants and animals that the human race has found a way to improve, and in which it develops new qualities. It is only after several generations that the improvement becomes complete. This is the perfect metaphor of the different lives of each human being.”