《淮南子·原道训》
察其所以然，在于不懂 乐 之含义，因而日复一日地伤害着心性，丧失了本该有的平和本性。
察其所以，不得其形，而日以伤生，失其得者也。
If this is investigated, its root lies in not understanding the meaning of joy, and thus damaging the nature of the heart day after day, losing the peace of mind that should be there.