Diamond has frequently drawn on the work of the Confucian sage Mencius (孟子, 372-289 BCE) in two interconnected ways: the belief in the inherent goodness of human nature which is core to both men’s philosophy; and the Mencian model of the Four Cardinal Virtues, which Diamond has incorporated into his own approach.
Regarding Mencius’ view of human nature, Wing-tsit Chan notes that “while Confucius no more than implied that human nature is good, Mencius declared definitely that it is originally good. Moreover, he built his entire philosophy on this tenet, and was the first to do so.” Diamond is particularly fond of, and has frequently quoted, a famous analogy from Mencius between the goodness of human nature and water:
“Human nature is good just as water seeks low ground. There is no man who is not good: there is no water that does not flow downward.”
The Cardinal Virtues are Zhi (智), Jen (also transliterated Ren, 仁), Yi (義) and Li (禮). Zhi, commonly translated as knowledge or wisdom, is in Diamond’s terms the state of Belovedness* – the feeling of feeling loved by the mother – our ultimate wisdom. Zhi actuates Jen, commonly translated benevolence or humaneness, which is what Diamond terms the Soul*, the deepest part of the self, that is pure love (and which for Mencius embodies the innate goodness of human nature discussed above). In other words, feeling our mother’s love enables us to find our own Soul. Following on, Yi, righteousness or goodness, is in Diamond’s terms the grateful return for that love, which he terms Cantillation*. The fourth Virtue, Li, propriety or proper ritual, is the eternal law that impels all this, the equivalent of what Diamond terms an endum*: something that is worthy to be acted upon for its own sake. For further discussion, see entry on Four Cardinal Virtues of Mencius* and the independent entries for each of the Virtues: Jen*, Li*, Yi*, and Zhi*.
- “It would well seem that Mencius was perhaps the most inspired – and so inspiring – of all philosophers. His basic belief was that our inherent natures are naturally loving just as it is the inherent nature of water to run downward.” (“Mencius: His Philosophy Inspired by His Mother?” [paper])
Timeline: Diamond first cites Mencius in terms of his view of human nature in 2008, and has regularly done so since. In terms of the Four Cardinal Virtues, Diamond has been developing his model since c. 2010. Until c. 2015, Li was assigned the role of Cantillation rather than Yi: the switch occurred in the middle of 2015, and the subsequent “endum” role for Li was developed in 2018.
 Wing-tsit Chan, A Source Book in Chinese Philosophy. New Jersey: Princeton U. P., 1963, pp. 49-50.
 Mencius: A Bilingual Edition, trans. D. C. Lau, rev. ed. (Hong Kong: The Chinese University Press, 2003), p. 241.