The danger of obedience

The words of C. S. Lewis in his book The Screwtape Letters (pg 40). This quote is from a conversation between two demons:

Our cause is never more in danger then when a human, no longer desiring, but still intending, to do our enemy’s [God’s] will, looks around a universe from which ever trace of him seems to have vanished, and asks why he has been forsakes, and still obeys.