One day, Confucius asked Zilu to prepare rain gear for him as he was going out. It rained heavily as expected after going out. Zilu asked Confucius how he knew it would rain today. Confucius said, "According to one ancient book, if the moon is far from the Bi star (one of the twenty eight stars of the Chinese constellations), it would rain heavily. I watched the stars last night and saw that the moon didn't stop near the Bi star, so I knew it was going to rain." One night a few days later, Zilu saw that the moon and the Bi star were connected by dark clouds. As Confucius was about to go out the next day, Zilu prepared rain gear for him. However, this time Confucius said no, and indeed it didn't rain that day. Zilu was confused and asked Confucius about it. Confucius replied, "That day, the Bi star was on the south side of the moon, so it would rain the next day. But last night, the Bi star was on the north side of the moon, so although there are dark clouds, it would not rain." What Confucius wanted to make Zilu understand is that the same truth would change according to different specific situations.