‘Niceness’—wholesome, integrated personality—is an excellent thing. We must try by every medical, educational, economic, and political means in our power to produce a world where as many people as possible grow up ‘nice’; just as we must try to produce a world where all have plenty to eat. But we must not suppose that even if we succeeded in making everyone nice we should have saved their souls. A world of nice people, content in their own niceness, looking no further, turned away from God, would be just as desperately in need of salvation as a miserable world—and might even be more difficult to save.
For mere improvement is not redemption, though redemption always improves people even here and now and will, in the end, improve them to a degree we cannot yet imagine. God became man to turn creatures into sons: not simply to produce better men of the old kind but to produce a new kind of man. It is not like teaching a horse to jump better and better but like turning a horse into a winged creature. Of course, once it has got its wings, it will soar over fences which could never have been jumped and thus beat the natural horse at its own game. But there may be a period, while the wings are just beginning to grow, when it cannot do so: and at that stage the lumps on the shoulders—no one could tell by looking at them that they are going to be wings—may even give it an awkward appearance.
C.S. Lewis, Mere Christianity (1952; Harper Collins: 2001) 215-216.