"Everyone knows what is useful, but doesn't know what is useless" means that people all know what is a temporary useful purpose, but don't know what is a temporary useless purpose. It means we need to look at things dialectically. In fact, this means that usefulness and uselessness are relative. Useless at this time does not mean useless forever. On the contrary, it is useful at this time, but it does not mean that it will always be useful. If we look at the essence of things dialectically and think from multiple angles, perhaps uselessness and usefulness are just problems of different attitudes towards things, and the effects reflected by things are different.

Source: "Everyone knows what is useful, but he doesn't know what is useless." This sentence comes from Zhuangzi? Human life. "

The original text is as follows: (excerpt)

Confucius visited Chu and Chu Kuang and said, "Phoenix is like a phoenix, why is it like the decline of virtue?" We can't wait for the afterlife, and we can't chase after it. There is a saying in the world, and a saint becomes a man; There is no road in the world, and saints have no way to live. At this time, I am just exempt from punishment! The blessing is as light as a feather, you don't know what it is; If the disaster is serious, I don't know how to avoid it Almost, almost! Treat people with virtue. Almost, almost! Draw the ground and follow. Fan Yang didn't hurt john young. I walk in the song without hurting my feet. "

Mountain wood, self-defeating; Fry yourself on fire. Guangxi is edible, so cut it; Paint can be used, so cut it. Everyone knows what is useful, but not what is useless.

When Confucius went to Chu, Jieyu, a hermit of Chu, deliberately came to Confucius' door and said, "Phoenix bird, phoenix bird! How can you come to this decadent country with great virtue! The future world can't be expected, and the past time can't be recovered. The rule of the world, the sage made a career; The monarch is dark, the world is in chaos, and saints have to go with the flow to survive. In today's era, fear can only avoid punishment and humiliation. Happiness is lighter than feathers, and I don't know how to get it; Evil is more important than the earth, and I don't know how to avoid it. Forget it, forget it! Don't preach your virtue in front of people! Danger. Danger. Artificially draw a road for people to follow! Thorns everywhere, don't hinder my walking! The winding road, don't hurt my feet! "

The trees on the mountain are cut down by themselves because there are ready-made materials, and the candles with oil spots are melted and fried by themselves because they can burn lighting. Cinnamon is fragrant and edible, so it is cut down. Because the tree paint can be used, it is chopped with a knife and axe. People all know the useful use, but they don't know the greater use of the useless.