There are three things that spread the Christ-life to us: baptism, belief, and… Holy Communion…. I cannot myself see why these things should be the conductors of the new kind of life. But then, if one did not happen to know, I should never have seen any connection between a particular physical pleasure and the appearance of a new human being in the world. We have to take reality as it comes to us: there is no good jabbering about what it ought to he like or what we should have expected it to be like. But though I cannot see why it should be so, I can tell you why I believe it is so.I have explained why I have to believe that Jesus was (and is) God. And it seems plain as a matter of history that He taught His followers that the new life was communicated in this way. In other words, I believe it on His authority. Do not be scared by the word authority. Believing things on authority only means believing them because you have been told them by someone you think trustworthy. Ninety-nine per cent of the things you believe are believed on authority. I believe there is such a place as New York. I have not seen it myself. I could not prove by abstract reasoning that there must he such a place. I believe it because reliable people have told me so. The ordinary man believes in the Solar System, atoms, evolution, and the circulation of the blood on authority—because the scientists say so. Every historical statement in the world is believed on authority. None of us has seen the Norman Conquest or the defeat of the Armada. None of us could prove them by pure logic as you prove a thing in mathematics. We believe them simply because people who did see them have left writings that tell us about them: in fact, on authority. A man who jibbed at authority in other things as some people do in religion would have to be content to know nothing all his life.
Quotes from Mere Christianity, Part 27
C.S. Lewis, Mere Christianity (1952; Harper Collins: 2001) 61-62.