Mere Christianity, in The Complete C. S. Lewis Signature Classics

pp. 34-35

“When we have understood free will, we shall see how silly it is to ask, as somebody once asked me, ‘Why did God make a creature of such rotten stuff that it went wrong?’  The better stuff a creature is made of—the cleverer and stronger and freer it is—then the better it will be if it goes right, but also the worse it will be if it goes wrong.  A cow cannot be very good or very bad; a dog can be both better and worse; a child better and worse still; an ordinary man, still more so; a man of genius, still more so; a superhuman spirit best—or worst—of all.”