Xiao, filial piety, is the obligation of children to their parents and, by extension, of the living to their ancestors. It is the most consequential single value in the Confucian tradition, and the Analects give it a foundational role: filial and fraternal duty are called the root of humaneness, on the reasoning that a person who is good to those closest to them is unlikely to rebel against superiors, and that virtue grows outward from the family rather than being applied to it from a general principle.
Its content is more demanding than obedience. The Analects insist that supporting parents materially is not enough, since one supports dogs and horses too, and that without reverence there is no difference between the two. They also require that a son remonstrate with a parent who is in the wrong, gently, and without abandoning respect if the remonstrance is rejected, which makes filial piety compatible with disagreement in a way that later practice often obscured. Mencius extended the analysis and treated the failure to produce descendants as the gravest of the unfilial acts, a statement with enormous social consequences over two millennia.
The Classic of Filial Piety, an early text heavily used in elementary education, systematised the doctrine and extended it explicitly from family to state, presenting service to the ruler as filial duty in another register. Filial piety thereby became the connective tissue of the Confucian political order, and it was reinforced institutionally: mourning obligations, including the three-year mourning for a parent that is debated within the Analects themselves, removed officials from office for extended periods, and imperial law treated offences against parents with special severity.
The tradition also generated popular literature pressing the value to extremes. The Twenty-Four Exemplars of Filial Piety circulated very widely and includes stories of self-mutilation and, notoriously, of a son proposing to bury his own child in order to feed his mother. These were criticised within the tradition as well as outside it.
Filial piety was a principal target of twentieth-century critiques of Confucianism, in the New Culture Movement and after, which held it responsible for gerontocracy, the subordination of women and the suppression of individual choice; Lu Xun's attack on the Twenty-Four Exemplars is the best known. It nonetheless remains a widely held value across East Asia, has been actively promoted by several governments facing rapidly ageing populations, and has been given legal expression, most visibly in the Chinese law of 2013 requiring adult children to visit elderly parents. Whether the value can be separated from the hierarchy it historically carried is a live question among contemporary scholars, and the answers given are not uniform.