有一次,著名的文艺评论家希尔伯特,不得不为一个朋友所著的书写一篇评论文章,他把评论文章写在一张纸的顶上方,把自己的签名写在最下方。在评论文章和签名之间有一块很大的空白。朋友问希尔伯特:“您留下这块空白是什么意思呢?” Once, famous literary critic Hilbert had to write a commentary for a friend’s book. He wrote the commentary on the top of a piece of paper and wrote his signature at the bottom. There is a big gap between the commentary and the signature. A friend asks Hilbert: “What do you mean by leaving this blank? ”