It is here that C. S. Lewis deviates from the original Greek myth. In the original, Psyche's sisters could see the castle. But for C.S. Lewis this phenomenon was inadequate as a metaphor for faith. Faith is the justified belief in things unseen. It is not a leap to believe in something rationally testable and tangible. If Orual is to find faith, she must believe in things she cannot see.
Till We Have Faces
by C. S. Lewis