Xin closes the set of Five Constants, Wu Chang, a grouping the Han dynasty Confucian scholar Dong Zhongshu is credited by later tradition with formally fixing as a set of five correlated with the five phases, wu xing, of Chinese cosmology, wood, fire, earth, metal and water, a correspondence that gave the ethical scheme a place within the broader Han synthesis of moral, political and natural philosophy rather than leaving it a purely ethical list detached from cosmology.
Sources of Chinese Tradition situates this systematisation as characteristic of Han dynasty scholarship generally, which frequently worked to align inherited Confucian ethical categories with the correlative cosmological frameworks dominant in the period, though the individual virtues ren, yi, li, zhi and xin each have earlier, independent attestation in the Analects and Mencius well before Dong Zhongshu's formal fivefold arrangement. Xin's place at the close of the set is read by some commentators as fitting, since trustworthiness in speech and action is what makes the other four constants, benevolence, righteousness, propriety and wisdom, externally verifiable and socially binding at all, a person's inward possession of the first four counting for little in practice if their word cannot be relied upon to reflect it.