This concept originated in The Book of Rites and Xunzi. The Confucian view is that human emotions arise naturally and need to be properly expressed. They have an inescapable influence on people’s conduct and their moral behavior. To maintain an orderly and stable moral order, it is important that the emotions of people are properly expressed and not indiscriminately suppressed. Therefore, moral standards should be based on people’s reasonable desire.

Why should the mourning period for one’s parents last for three years? The answer is that it is based on the degree of the mourner’s grief. Such a rule, which determines the order of human relations and differentiates the closeness between people and their social positions, should not be altered by cutting it short or extending it longer at will. (The Book of Rites)