If God was prepared to let us off, why on earth did He not do so? And what possible point could there be in punishing an innocent person instead? None at all that I can see, if you are thinking of punishment in the police-court sense. On the other hand, if you think of a debt, there is plenty of point in a person who has some assets paying it on behalf of someone who has not. Or if you take 'paying the penalty', not in the sense of being punished, but in the more General sense of 'standing the racket' or 'footing the bill', then, of course, it is a matter of common experience that, when one person has got himself into a hole, the trouble of getting him out usually falls on a kind friend.
Now what was the sort of 'hole' man had got himself into? He has tried to set up on his own, to behave as if he belonged to himself. In other words fallen man is not simply an imperfect creature who needs improvement: he is a rebel who just lay down his arms. Laying down your arms, surrendering, saying you are sorry, realising that you have been on the wrong track and getting ready to start life over again from the ground floor - that is the only way out of your 'hole'. This process of surrender - this movement full speed astern - is what Christians call repentance. Now repentance is no fun at all. It is something much harder than merely eating humble pie. It means I'm learning all the self-conceit and self-will that we have been training ourselves into for thousands of years. It means killing part of yourself, undergoing a kind of death. In fact, it needs a good man to repent. And here comes the catch. Only a bad person needs to repent: only a good person can repent perfectly. The worse you hard the more you need it and the less you can do it. The only person who could do it perfectly would be a perfect person - and he wound not need it.