what is the evidence is there that scout and jem are quite innocent at the beginning of the novel

At the beginning of the novel, Scout and Jem's world is indeed quite innocent, almost idyllic. Their summers seem warm and endless with role playing games, stories, and back yard adventures. Their view of the world is seen through the lens of innocence. They think, for example, that Boo is a nocturnal monster and that there is a safe zone until the Radley house.