Once there was a monk who specialized in the Buddhist precepts, and he kept to them all his life. Once when he was walking at night, he stepped on something. It made a squishing sound, and he imagined he had stepped on an egg-bearing frog.
This caused him no end of alarm and regret, in view of the Buddhist precept against taking life, and when he finally went to sleep that night he dreamed that hundreds of frogs came demanding his life.
The monk was terribly upset, but when morning came he looked and found that what he stepped on was an overripe eggplant. At that moment his feeling of uncertainty suddenly stopped, and for the first time he realized the meaning of the saying that “there is no objective world.” Then he finally knew how to practice Zen.