One day, Mozi severely reproached one of his disciples, Geng Zhuzi.
Geng Zhuzi felt wronged and complained, "I have not made more mistakes than others. Why did you reprimand me so harshly?"
Upon hearing this, Mozi said, "If you were to drive a swift horse and a goat up Mount Taihang, which one would you whip, the horse or the goat?"
Geng Zhuzi replied, "The swift horse, of course."
Mozi then asked, "Why the swift horse?"
Geng Zhuzi answered, "Because the swift horse is worth whipping; the goat is not."
Mozi concluded, "You are like the horse, not the goat, and worth reproaching. That is why I reproached you."