When Mencius came to the State of Song, he found that the Song Monarch was surrounded by only a few good ministers. So he planned to leave. Dai Bu-sheng, a high-ranking Song official, thought Mencius to be a man of exceptional talent, and did not want to see him leave. So, he told Mencius, “If you feel that there are too few good ministers serving the king, let me recommend Xue Ju-zhou to the king. He is a fine and upright man. Let us serve the State of Song together. What do you think?”

Mencius shook his head. Then, he sighed and said, “You wish for your king to become a wise and virtuous ruler, am I right? However, let me give you an example: if an official of Chu wishes his son to speak the Chi language, do you think he should hire a tutor from Chi or a tutor from Chu?” 

Dai Bu-sheng replied, “He should hire a tutor from Chi, of course!” Mencius then said, “If he hired a tutor from Chi, but his son was surrounded by Chu people who spoke the Chu language all day, it would be impossible for his son to learn how to speak the Chi language, no matter how hard the tutor tried. However, if you take his son to the State of Chi to live there for a couple of years, no matter how hard you try, it would be impossible for his son to speak the Chu language.”

Mencius looked at Dai Bu-sheng and said, “You say that Xue Ju-zhou is a fine and upright man, and wish to enlist his help to counsel the king. However, if all the king’s ministers were as good as Xue Ju-zhou, regardless of age or rank, it would be impossible for the king to do bad things. On the other hand, if all the king’s ministers were corrupt, regardless of age or rank, it would be impossible for the king to do good things. Do you think Xue Ju-zhou alone can make the king wise and virtuous?” Upon hearing this, Dai Bu-sheng could only nod and agree with what Mencius said.

孟子到了宋國後，發現宋國國君身邊的良臣很少，於是打算離開宋國。宋國大臣戴不勝覺得孟子是個人才，不想讓他離開，就對孟子說：「你覺得良臣不多不要緊，我會推薦薛居州給國君，這個人很不錯的，大家一起為宋國努力怎麼樣？」

孟子搖搖頭，嘆了一口氣說： 「你是希望國君變得賢明吧？我直接告訴你，如果有一個楚國大臣希望他的兒子會說齊國話，你覺得他應該找齊國人來教他呢，還是找楚國人來教他呢？」

戴不勝回答：「當然是請齊國人來教。」孟子又說：「如果他請了齊國人來教，但是孩子身邊總是有很多楚國人，一直在說楚國話。這樣就算是天天打他，要他學會齊國話，根本不可能。但如果帶他到齊國大街上住個幾年，就算天天打他，逼他一定要講楚國話，也根本不可能。」

孟子看看戴不勝，接著說：「雖然你說薛居州是一個好人，要讓他在國君的身邊做事。但是如果國君身邊的人無論年紀大小，地位高低都是薛居州那樣的好人。那麼國君會和誰去做壞事呢？ 但如果在國君身邊的人無論年紀大小，地位高低都不是薛居州那樣的好人，那國君又能和誰一起去做好事呢？一個薛居州，就能讓國君變好嗎？」戴不勝聽了，只能點點頭，同意孟子的話。