Correcting Our Arithmetic: by CS Lewis from Mere Christianity

I will set out and go back to my father and say to him: Father, I have sinned against heaven and against you.  I am no longer worthy to be called your son; make me like one of your hired men.'
 So he got up and went to his father. "But while he was still a long way off, his father saw him and was filled with compassion for him; he ran to his son, threw his arms around him and kissed him. "The son said to him, 'Father, I have sinned against heaven and against you. I am no longer worthy to be called your son.' Luke 15:18-21

Would you think I was joking if I said that you can put a clock back, and that if the clock is wrong it is often a very sensible thing to do? .... We all want progress. But progress means getting nearer to the place where you want to be. And if you have taken a wrong turning, then to go forward does not get you any nearer. If you are on the wrong road, progress means doing an about-turn and walking back to the right road; and in that case the man who turns back soonest is the most progressive man. We have all seen this when doing arithmetic. When I have started a sum the wrong way, the sooner I admit this and go back and start again, the faster I shall get on. There is nothing progressive about being pig headed and refusing to admit a mistake. And I think if you look at the present state of the world, it is pretty plain that humanity has been making some big mistake. We are on the wrong road. And if that is so, we must go back. Going back is the quickest way on.