The current of thought later known as the School of Yin-Yang arose in ancient China during the Warring States era, a time when many thinkers were seeking a unifying vision of cosmos and society. Its emergence is usually located in the later phase of the Zhou dynasty, especially the Warring States period, when reflection on the patterns of heaven, earth, and human life intensified. Within this ferment, yin and yang were not yet a rigid doctrine but living symbols of complementary forces—dark and light, passive and active, receptive and creative—through which sages sought to read the rhythms of reality. The school did not appear out of thin air; it crystallized from a long maturation of ideas already circulating in earlier texts and traditions.

Among these earlier sources, the Book of Changes (Yijing or I Ching) and related cosmological reflections played a pivotal role. In that classic, the interplay of broken and unbroken lines, of yielding and firm, already hints at a worldview structured by polarity and transformation. Over time, such insights were joined with reflections on the Five Phases—wood, fire, earth, metal, and water—understood not merely as substances but as recurring processes and cycles. These strands of thought, initially scattered and unsystematic, provided the raw material for a more comprehensive cosmology.

The figure most closely associated with giving this diffuse heritage a coherent shape is Zou Yan, who is traditionally regarded as the founder and principal systematizer of the School of Yin-Yang. Drawing on inherited notions of yin and yang and the Five Phases, he articulated a grand pattern in which cosmic change, natural phenomena, and political order could be seen as expressions of a single underlying rhythm. Under his hand, yin–yang and Five Phases theory became a framework for understanding not only the alternation of seasons and celestial movements, but also the rise and fall of ruling houses and the legitimacy of dynastic succession. What had been scattered insights about the play of opposites and cycles of transformation thus coalesced into a distinct school of thought.

Viewed in this light, the origin of the School of Yin-Yang can be seen as both historical and spiritual: historically rooted in the intellectual milieu of the Warring States, and spiritually grounded in a contemplative attention to the patterned flow of the cosmos. It arose from careful observation of natural cycles and from a desire to discern the hidden order that binds heaven, earth, and human affairs into a single tapestry. By weaving together yin and yang with the Five Phases, its early architects offered a vision in which change itself becomes the primary teacher, and harmony is found not in escaping flux but in understanding and aligning with its ceaseless transformations.