In Chinese philosophy, a taijitu () is a symbol or diagram () representing Taiji () in both its monist (wuji) and its dualist (yin and yang) aspects. Such a diagram was first introduced by Neo-Confucian philosopher Zhou Dunyi (; 1017–1073) of the Song Dynasty in his Taijitu shuo (). The modern Taoist canon, compiled during the Ming era, has at least half a dozen variants of such taijitu. The two most similar are the "Taiji Primal Heaven" () and the "wuji" () diagrams, both of which have been extensively studied during the Qing period for their possible connection with Zhou Dunyi's taijitu. Ming period author Lai Zhide (1525–1604) simplified the taijitu to a design of two interlocking spirals. In the Ming era, the combination of the two interlocking spirals of the taijitu with two black-and-white dots superimposed on them became identified with the He tu or "Yellow River diagram" (). This version was reported in Western literature of the late 19th century as the "Great Monad", and has been widely popularised in Western popular culture as the "yin-yang symbol" since the 1960s. The contemporary Chinese term for the modern symbol is "two-part Taiji diagram". Ornamental patterns with visual similarity to the "yin-yang symbol" are found in archaeological artefacts of European prehistory; such designs are sometimes descriptively dubbed "yin yang symbols" in archaeological literature by modern scholars. Structure The taijitu consists of five parts. Strictly speaking, the "yin and yang symbol", itself popularly called taijitu, represents the second of these five parts of the diagram. At the top, an empty circle depicts the absolute (Wuji) A second circle represents the Taiji as harboring Dualism, yin and yang, represented by filling the circle in a black-and-white pattern. In some diagrams, there is a smaller empty circle at the center of this, representing Emptiness as the foundation of duality. Below this second circle is a five-part diagram representing the Five Agents (Wuxing), representing a further stage in the differentiation of Unity into Multiplicity. The Five Agents are connected by lines indicating their proper sequence, Wood (木) → Fire (火) → Earth (土) → Metal (金) → Water (水). The circle below the Five Agents represents the conjunction of Heaven and Earth, which in turn gives rise to the "ten thousand things". This stage is also represented by the Eight Trigrams (Bagua). The final circle represents the state of multiplicity, glossed "The ten thousand