In the 11th year of the reign of Duke Ai of Lu state, Confucius was 68 years old and in Wei state. Lord Ji Kangzi, the ruling minister of Lu state, sent people with gifts to invite Confucius to return home. Confucius returned home and wrote a song of hills. The main idea of the song is as follows: The high hill that I climbed was with tortuous hillside. Benevolence seemed very close to catch, but it was far from being achieved. I didn't know how to walk on, and I was bound by difficulties and hardships. Looking back with a sigh, the Mount Tai towered into the clouds with lush trees, and Liangfu (a hill at the foot of Mount Tai) was connected with it. With the road full of thorns, I wanted to climb Mount Tai, but I couldn't make it. I wanted to cut the thorns but I didn't have an axe, and I feared that they will breed and spread. The only thing I could do was to sigh and shed my tears.