春秋时期，鲁国有个能工巧匠公输子，人称“鲁班”。他用竹木造了一只喜鹊。

这只木制的喜鹊，安装着机关。只要一开动它，就能像真的鸟一样展翅高飞。它一连飞了三天三夜才降落下来。

公输子非常欣赏自己这件得意的作品。

墨子知道了这件事情以后，立刻去见公输子，对他说：

“你知道，普通的木匠只花很短的时间，用极少的木料就能做成车辖。将车辖插在车轴的两端，这样的车子可以装载许多东西，能经受五十石的重压。而这只你费了心血做成的木头喜鹊，虽然会飞也很漂亮，但是却不如车辖那样有实用价值。木匠做出来的东西，要对人们的生活有帮助，大家才会夸他心灵手巧;否则难免被人笑骂。”

During the Spring and Autumn Period (770-476B.C), a skillful craftsman named Gongshu Zi in the State of Lu, Known to people as "Lu Ban", made a magpie with bamboo and wood.

A machine was installed in this magpie which, when started, could fly high like a real bird. It actually flew continually for three days and nights before it landed.

Gongshu Zi greatly appreciated this excellent work of his own.

When Mo Zi (Master of the Mohist School ) heard of this, the went immediately to see Gongshu Zi and said to him:

"As you know, it takes an ordinary carpenter a very short time to make a linchpin of a wheel with the minimum amount of timber. A vehicle with a linchpin inserted into each end of an axle can carry many things and bear a heavy load of 50 dan(1 hectolitre.)" But you took painstakingeffort to make this wooden magpie. Thought pretty and able to fly, it cannot compare with the linchpin in terms of practical value. Things made by a carpenter should be useful for people's life, so that everyone will praise him for his cleverness and skill. Otherwise, he is bound to bederided.