No aristocrat would sit in the wild grass to dream. Aristocrats have gardens for that, if they dream at all. - Sheri S. Tepper

Since they were not in the Dicta, knowledge of them would be considered evidence of heresy, or of imagination, which was almost as bad.

Our religion is based upon eschewing human sacrifice in favor of lives that are fulfilling, productive, and joyful."
Startled, Ellin cried, "Human sacrifice! I am surprised you can think of such a thing!"
D'Jevier said with unfeigned weariness, "My dear young woman, our history is made up of millennia of human sacrifice. Well into the twenty-first century, huge armies of young men were sacrificed to tribal or national honor, women were sacrificed to male supremacy, children were sacrificed to brutality, all immolated in flames of painful duty. We try to determine whether the dutiful will suffer and to decide how that suffering may be compensated. We continually redesign our society to provide joy to those who incur pain on our behalf.

My son, be schooled by me. If your people taught you when you were a child that there are monsters in the wood, you would have believed them. Then, later, if a woodsman had come and said to you, leading you among the trees, 'See, there is nothing here but shadow and light, leaf and trunk, bird and beast. See, I show you. Look with your own eyes.' Though you would look and see nothing, still you would believe there were monsters there. You would believe them invisible, or behind you, or hiding beneath the stones, or within the trees somehow. No matter what the woodsman said, you would believe your fear. Men always believe their fear. Only the strong, the brave, the curious—only they can overcome their fear to peer and poke and pry at life to find what is truly there…