What has always surprised me when I walk into a bookstore is the number of books that you can find that are written with certainty. The authors tell some story as though it's true, but they don't have any evidence that it is true!
“If we had a keen vision of all that is ordinary in human life, it would be like hearing the grass grow or the squirrel's heart beat, and we should die of that roar which is the other side of silence.”