"An Ever Increasing Craving for an Ever Diminishing Pleasure Is the Formula"

From C. S. Lewis's The Screwtape Letters (p. 44)--remember that it's told from a devil's point of view, so "the Enemy" is God and "Our Father" is Satan.

Never forget that when we are dealing with any pleasure in its healthy and normal and satisfying form, we are, in a sense, on the Enemy’s ground. I know we have won many a soul through pleasure. All the same, it is His invention, not ours. He made the pleasures: all our research so far has not enabled us to produce one. All we can do is to encourage the humans to take the pleasures which our Enemy has produced, at at times, or in ways, or in degrees, which He has forbidden. . . . An ever increasing craving for an ever diminishing pleasure is the formula. . . . To get a man's soul and give him nothing in return--that's what really gladdens Our Father's heart.