Your man has been accustomed, ever since he was a boy, to have a dozen incompatible philosophies dancing about together inside his head. He doesn’t think of doctrines as primarily “true” of “false”, but as “academic” or “practical”, “outworn” or “contemporary”, “conventional” or “ruthless”. Jargon, not argument, is your best ally in keeping him from the Church.
Don’t waste time trying to make him think that materialism is true! Make him think it is strong, or stark, or courageous—that it is the philosophy of the future. That’s the sort of thing he cares about…
By the very act of arguing, you awake the patient’s reason; and once it is awake, who can foresee the result? Even if a particular train of thought can be twisted so as to end in our favour, you will find that you have been strengthening in your patient the fatal habit of attending to universal issues and withdrawing his attention from the stream of immediate sense experiences. Your business is to fix his attention on the stream. Teach him to call it “real life” and don’t let him ask what he means by “real”.
C.S. Lewis, The Screwtape Letters