Screwtape is a senior demon writing to his nephew, Wormwood, who is an apprentice. Their ”father below” is the Devil and the ”enemy” is God. Screwtape writes these letters to train his nephew in how best to corrupt their ”patient’s” souls.
“Indeed the safest road to Hell is the gradual one–the gentle slope, soft underfoot, without sudden turnings, without milestones, without signposts,…Your affectionate uncle, Screwtape.”
“It is funny how mortals always picture us as putting things into their minds: in reality our best work is done by keeping things out.”
“Gratitude looks to the Past and love to the Present; fear, avarice, lust, and ambition look ahead. For the Present is the point at which time touches eternity.”
“Your patient has become humble; have you drawn his attention to the fact? All virtues are less formidable to us once the man is aware that he has them, but this is specially true of humility.”
“All is summed up in the prayer which a young female human is said to have uttered recently: “O God, make me a normal twentieth-century girl!” Thanks to our labors, this will mean increasingly: “Make me a minx, a moron, and a parasite.”
“Surely you know that if a man can’t be cured of churchgoing, the next best thing is to send him all over the neighbourhood looking for the church that “suits” him until he becomes a taster or connoisseur of churches.”
”Aggravate the most useful human characteristics, the horror and neglect of the obvious. You must bring him to a condition in which he can practise self-examination for an hour without discovering any of those facts about himself which are perfectly clear to anyone who has ever lived in the same house with him or worked in the same office.”
and so on.
Here is a very enjoyable reading of the letters by John Cleese, one tube leads into the next…
and here is the written material in full from Gutenberg