Liu Zongyuan, a celebrated Tang Dynasty writer, passed the imperial exam in 793 AD and became a court official. After joining a failed political reform, he was exiled to Yongzhou as a minor military advisor.
While serving as the Vice Governor of Yongzhou, Liu Zongyuan received a letter from a young man named Wei Zhongli, who proposed to become his disciple. At the time, the tradition of seeking a master for study had vanished; anyone who took on students to teach would face harsh criticism, and the student himself would be scorned. Moved by Wei Zhongli's courage to defy convention, Liu Zongyuan wrote a reply—this became the famous "Letter to Wei Zhongli on the Way of the Teacher."
Liu Zongyuan wrote in his reply:
“Ignorance breeds astonishment—this is common. I never believed the tale of Sichuan dogs barking at the sun, but after arriving in Yongzhou and seeing dogs there bark wildly at snow—something they had never seen—I finally understood.”
"Ancient custom required men to undergo a capping ceremony at age twenty, but this practice had not been popular for centuries. Recently, a young man named Sun Changyin performed the ceremony, only to be ridiculed by his colleagues."
“These two examples show just how stubborn worldly conventions can be. In such an environment, you have broken through the norm by asking to become my student—I am deeply moved. So, I am willing to share my insights on writing with you. When I was young, I believed that elegant language alone made a good essay. But as an adult, I realized that only writing with depth of thought is truly excellent. Therefore, no matter what I write, I never dare to take it lightly. I strive to make my work as plain and honest as the *Book of Documents*, as timeless as the *Book of Songs*, as reasonable as the *Book of Rites*, as clear in right and wrong as the *Spring and Autumn Annals*, and as full of change as the *Book of Changes*.”
After receiving Liu Zongyuan's guidance and inspiration, Wei Zhongli's studies advanced by leaps and bounds, and he later passed the imperial examination to become a jinshi.
Later, the idiom "to treat with indifference" came to describe a careless attitude toward matters.
Source: Liu Zongyuan (Tang Dynasty), *Reply to Wei Zhongli on the Way of the Teacher*
Meaning of the Idiom: Later, the Chinese idiom "掉以轻心" came to describe a careless attitude toward matters.