The Screwtape Letters (1-62)

This book, The Screwtape Letters, by C.S. Lewis, is a fictional story about two demons writing letters back and forth. The uncle, Screwtape, is mentoring his nephew, Wormwood, on how to do the main job of a demon, bringing humans away from "the Enemy", the Christian God. In one of my favorite letters, Screwtape is telling Wormwood about the undulation of human faith, how it reaches peaks and troughs.

And that is where the troughs come in. You must have wondered why the Enemy does not make more use of His power to be senseibly present to human souls in any
degree He chooses and at any moment. But you now see that the Irresistible and
the Indisputable are the two weapons which the very nature of His scheme forbids
Him to use. Merely to over-ride a human will (as His felt presense in any but
the faintest and most mitigated degree would certainly do) Would be for him
useless. He cannot ravish. He can only woo. For His ignoble idea is to eat the
cake and have it; the creatures are to be one with him, but yet themselves;
merely to cancel them, or assimilate them, will not serve. (46)

Lewis makes a very interesting point in this passage, which i feel like i need to first explain with a quote from the prolouge; "For of course [the book's] puprose was not to speculate about diabloical life but to throw light from a new angle on the life of men". He is saying that he is not saying to convert to Satanism, but to look at Christianity in a new way. He is saying not to loose hope during these "trough periods" of one's faith, but to remember in both the troughs and peaks to look for God. God cannot make you believe in him, but he must show people that he is the better way, and not to turn to tempation.

Lewis, C.S. The Screwtape Letters Westwood, New Jersey: Barbour and Company, Inc. 1961