Do not be scared by the word authorithy. Believing things on ly 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 authorithy. 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 be 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 ciculation 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 authorithy. A man who jibbed at authorithy in other things as some people do in relifion would have to be content to know nothing all his life.