During the Spring and Autumn period, Duke Li of Jin was a foolish and extravagant ruler who distrusted his powerful ministers and plotted to replace them with his favorites.
In 574 BCE, Duke Li of Jin, urged on by his advisor Xu Tong, executed the three Xi brothers—Xi Qi, Xi Chou, and Xi Zhi—all high-ranking ministers, and displayed their bodies at court. Xu Tong then led soldiers to arrest Luan Shu and Zhonghang Yan right there in the court. Feeling that executing five ministers in a single day would look bad, the Duke released the two men, telling them to forget the matter and keep their posts. He then appointed Xu Tong as a minister.
Luan Shu and Zhonghang Yan nursed their grievances, and soon, taking advantage of Duke Li of Jin's outing for pleasure, they seized him and executed Xu Tong.
In the first month of the following year, Luan Shu and Zhonghang Yan sent men to kill Duke Li of Jin, then brought Zhouzi from the Zhou king's capital to install him as the ruler of Jin. Zhouzi, also known as Sun Zhou, was the great-grandson of Duke Xiang of Jin. Though only fourteen at the time, he was intelligent and capable. When the Jin ministers came to welcome him, Zhouzi said:
"I never originally desired to become a ruler—now that I've reached this position, perhaps it is Heaven's will! People demand a ruler to issue commands, yet once a ruler is established, they refuse to obey him. What use is such a ruler? If you gentlemen wish to employ me, I will be your ruler today; if not, so be it. But if you install a ruler, you must respectfully heed his commands."
The ministers all said, "You preside over state affairs—that is our wish. How dare we not follow your commands!"
After Zhouzi became ruler, known as Duke Dao of Jin, he immediately expelled seven officials who had failed to uphold their duties as subjects.
The Zhou family had an elder brother, so why wasn't he made the ruler? According to the *Zuo Commentary*, Zhou's older brother was so dim-witted he couldn't tell beans from wheat, making him unfit to be a sovereign.
Later, the idiom "Unable to Distinguish Beans from Wheat" came to describe ignorance, and now also refers to lacking practical knowledge due to being out of touch with production practices.
Source: *Zuo Zhuan*, Chapter "The Eighteenth Year of Duke Cheng"
Meaning of the Idiom: Later, the Chinese idiom "不辨菽麦" came to describe ignorance, and now also refers to lacking practical knowledge due to being out of touch with production practices.