春秋时代，宋国有一个人，养了一大群猴子。这些猴子能够听懂主人说的话。过了一段时间，主人家里穷了，想限制一下猴子每天吃的粮食。于是对猴子说：“每天给你们吃的橡子，早上三个，晚上四个，够了吗？”猴子们听了，都怒气冲冲地站了起来，主人又说：“早上四个，晚上三个，够了吗？”猴子们听了，都趴在地上表示满意。
“朝三暮四”原来表示欺骗和愚弄的手段，后来改用来比喻说话、做事反复无常。
 
 
Three in the Morning and Four in the Evening
 
In the Spring and Autumn Period, a man in the state of Song raised monkedy. The monkeys could understand what he said. As the man became poor, he wanted to reduce the monkey's food. He first suggested that he give them three acorns in the morning and four acorns in the evening. thereupon, the monkeys protested angrily. Then their owner said"How about fourn in the morning and three in the evening?" The monkeys were satisfied with that.
This idiom originally meant to befool others with tricks. Later it is used to mean to keep changing ones' mind.