"If you want to get the hang of it, think how you would like to become a slug or a crab."

In C. S. Lewis: A Biography (New York: W. W. Norton & Company, 1990), A. N. Wilson takes issue with Lewis's analogy here.

Nor are all his attempts at analogy helpful. Certainly to explain the Incarnation in a quarter of an hour over the air is a tall order, but Lewis could surely have done better than to say, "If you want to get the hang of it, think how you would like to become a slug or a crab." Apart from being offensive, this is bad theology. God made human beings in His own image and likeness. Human beings did not make slugs or crabs. Man could not "redeem" the slugs even if slugs were in need of redemption.