The Doctrine of the Mean makes remarkable claims for sincerity (cheng): the one who has made himself wholly sincere, fully realising his own nature, can thereby help to realise the nature of others and of all things, and so "may assist the transforming and nourishing powers of Heaven and Earth" and "form a trinity" with them. Moral self-perfection is thus given a cosmic dimension, the fully realised human being becomes a co-worker with the universe itself.
Like the Great Learning, the text owed its later prominence to Zhu Xi (1130-1200), who included it among the Four Books, placing it last as the most advanced and subtle, and furnished it with a commentary that made its metaphysics central to Neo-Confucian thought about human nature, the cosmos, and the sagehood attainable through cultivation. Through the Four Books it became part of the foundation of Chinese education and of the civil service examinations until 1905, and it deeply shaped Confucian philosophy across East Asia. Scholars regard the Doctrine of the Mean as the most metaphysical of the Four Books and as a key source for Confucian reflection on the relation between the moral and the cosmic order.