Quote what does the inspector says is the relationship between the devil and deveation?

"The Devil sends Deviations among us to weaken us and tempt us away from Purity. Sometimes he is clever enough to make a nearly-perfect imitation, so we have always to be on the look-out for the mistake he has made, however small, and when we see one it must be reported at once. You'll remember that in future, won't you?"