This was a commonplace, and I think I got it from Flannery O’Connor: A Proper Scaring
…In Flannery O’ Connor’s personal copy of William James The Varieties of Religious Experience: A Study in Human Nature, she marked the following passage. “In the Louvre there is a picture by Guido Reni of St. Michael with his foot on Satans neck. The richness of the picture is in large part due to the fiend’s figure being there. The richness of its allegorical meaning also is due to his being threre — that is, the world is all the richer for having a devil in it, so long as we keep our foot upon his neck. In the religious conciousness, that is just the position in which the fiend, the negative or tragic principle is found.”

…From the very creation account we are presented with an optomistic eschatology. Each day of creation is ended with “evening and morning”. I find it interesting that is isn’t morning and evening. The darkness is followed by light even from as early as creation.