Wormwood is a devil in training under his Uncle Screwtape’s coaching by mail. Wormwood’s “patient” is a young man, who has been recently united to Christ by faith in the Gospel.
“All you then have to do is to keep out of his mind the question ‘If I, being what I am, can consider that I am in some sense a Christian, why should the different vices of those people in the next pew prove that their religion is mere hypocrisy and convention?’ You may ask whether it is possible to keep such an obvious thought from occurring even to a human mind. It is, Wormwood, it is!”
By Screwtape’s tenth letter he simply says: “All mortals tend to turn into the thing they are pretending to be. This is elementary.”
A true sense of who you are as a Christian will never come to our minds if you fail to keep two things in mind: 1) You must never give anyone but Christ the authority to tell you who you are. 2) You must never pretend to be someone you are not.
Lewis, C. S. (2009-05-28). The Screwtape Letters (pp. 8, 46). HarperCollins. Kindle Edition.