What is the concept of good in The Wizard of Oz?

According to The Wizard of Oz, the doers of evil may be craftier in their own time than the doers of good. But that doesn't mean victory. For the original book, and the 1939 film version, of The Wizard of Oz are on the side of the goodness and innocence of Dorothy Gale and her four friends over the evil and delusions of the witch-driven hordes of wolves, enslaved Winkies, crows and bees; the Wicked Witches of the East and of the West; the part-bear part-tiger Kalidahs; the Great Yellow Wildcat; the Giant Spider; and the Fighting Trees. As the Leader of the Winged Monkeys says upon seeing the protective mark from the kiss of the Good Witch of the North on Dorothy's forehead, ... the Power of Good ... is greater than the Power of Evil."