《荀子·乐论》
况且音乐，是协调人情时不可变更的手段；礼制，是治理社会时不可更换的原则。
且乐也者，和之不可变者也；礼也者，理之不可易者也。
Moreover, music is an unchangeable method for harmonising human feelings; rites are an unalterable principle for governing a society.