In Zhou Dunyi’s Taoist‑Confucian cosmology, Wuji and Taiji name two inseparable aspects of the same ultimate reality. Wuji, literally “limitless,” designates the absolute, formless, undifferentiated ground that precedes all distinctions and all phenomenal existence. It is not a mere blank nothingness, but an inexhaustible reservoir of potential that has no polarity, no movement versus stillness, no yin versus yang. Taiji, the “Great Ultimate,” is that very same reality as it begins to function, as it turns toward manifestation and order. When Zhou Dunyi speaks of “Wuji er Taiji” – “Wuji, and yet Taiji” – he is pointing to this paradox: the one ultimate is at once beyond all differentiation and already the source of all differentiation.

From this perspective, Taiji can be understood as Wuji in activity, the first principle of manifestation and differentiation. As Taiji “moves and generates yang” and “in its utmost stillness generates yin,” it gives rise to the polarity of yin and yang, then to the Five Phases, and finally to the “ten thousand things.” Wuji thus provides the unchanging, absolute foundation, while Taiji serves as the dynamic, creative principle that initiates and orders the cosmological process. Yet this is not a strict dualism or a simple temporal sequence; it is a way of viewing one reality from two angles. Seen as sheer, undifferentiated suchness, it is called Wuji; seen as the generative, structuring principle of cosmic process, it is called Taiji.

This relationship also carries an implicit vision of spiritual cultivation. Because Taiji is the principle by which the cosmos unfolds, and because human heart‑mind participates in this same ordering principle, ethical and spiritual practice can be understood as aligning oneself with Taiji’s pattern. At the same time, the ultimate ground of this pattern is Wuji, the limitless and undifferentiated source in which all distinctions are rooted and to which all manifestations ultimately return. To contemplate Wuji and Taiji together is to see that the stillness at the heart of things and the ceaseless movement of creation are two sides of a single mystery.