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.
Source: Mere Christianity