What is the story of Emperor Tiandi killing dragons?

On his way to the northern state of Qi, Mozi met a fortune-teller Mr. Yin and Yang. Master Yin and Yang said to Mozi, "Emperor Tian just killed the black dragon in the north today. Mr. Yin has dark skin, so don't go to the north."

Mozi refused to listen to the teacher of Yin and Yang and resolutely continued to move north. However, after arriving at the south bank of Zishui, Shandong Province, it happened that the river surged and it was impossible to ferry, so we had to go back the same way.

Master Yin and Yang saw Mozi again and proudly boasted, "Sir, I told you not to go to the North." Now it turns out that my prediction is correct. "

Mozi disagreed. He retorted, "Now southerners can't go to the north, and northern Renye Fang can't come to the south. In fact, their skin colors are different, some are black and some are white. Why can't they get what they want? This is only because of the barrier caused by the surge of water. Besides, according to your theory, the Emperor of Heaven slaughtered Qinglong in the east, Red Dragon in the south, White Dragon in the west and Black Dragon in the north every day. In this way, people all over the world can't travel long distances. Doing so will not only go against people's wishes, but also make the world empty and accomplish nothing. Therefore, your lies are really unacceptable! "

Mozi refuted the superstition of Yin and Yang teachers with a simple materialistic point of view. This fearless spirit based on respecting science and facts is worth learning and developing.