Ray Bradbury said this quote
“ That's what I want, a mental evidence I can feel. I don't want physical evidence, proof you have to go out and drag in. I want evidence that you can carry in your mind and always touch and smell and feel. But there's no way to do that. In order to believe in a thing you've got to carry it with you. You can't carry the Earth, or a man, in your pocket. I want a way to do that, carry things with me always, so I can believe in them. How clumsy to have to go to all the trouble of going out and bringing in something terribly physical to prove something. I hate physical things because they can be left behind and become impossible to believe in them. ”