Taiji

The Taiji (太極), the 'Supreme Ultimate' in Taoism, is understood to be the highest conceivable principle from which existence flows. In contemporary terms, the Taiji is the infinite, essential, and fundamental principle of evolutionary change which actualizes all potential states of being through the self-organizing integration of complementary existential polarities. More simply, it is the co-substantial union of 'yin' and 'yang,' the two opposing qualities of all things. In order for 'hot' to exist, so must 'cold.' The existence of 'hot,' in fact, is wholly dependent on the existence of 'cold' and ultimately arises from it, just as the existence of 'cold' in turn arises from that of 'hot' and is wholly dependent thereupon.

Note that as the highest conceivable principle, the Taiji is still superseded by the Tao itself, the inconceivable essence of reality, which is by nature ineffable and beyond description. This 'ultimate reality' is that which cannot be named, although through conceptualizations such as the Taiji, the Tao can be approached.