Beyond "Taiji": The Dao-Er Foundation of Yin-Yang Metaphysics

Yin-Yang theory, as the core of traditional Chinese cosmology, has long been interpreted within the monistic framework of "Taiji begets Liangyi", which has led to Yin and Yang being regarded as mere derivatives of "the One". Based on Dao-Er ontology, this paper reconstructs the metaphysical status of Yin and Yang: they are not differentiated from "the One", but rather a direct manifestation of the Dao-Er ontology at the cosmological level. The fundamental relationships between Yin and Yang—complementarity, interdependence, transformation, and mutual inclusion—are essentially cosmological expressions of the primordial dual structure. By reinterpreting the saying "One Yin and one Yang are called the Dao" and the Taiji Diagram, this paper argues for the primordial status of Yin and Yang, completing the systematic transition of Dao-Er philosophy from ontology to cosmology. It establishes a new paradigm of Chinese cosmology that takes duality as its first principle.