Taiji(the supreme ultimate) has three different meanings. First, it refers to the origin of the world. The ancient Chinese saw it either asqi(vital force) oryuanqi(primordial vital force) that permeates the chaotic world, or as a universal principle, i.e.Dao（道）orli (理), or aswu (无). Second, it is used as a term of divination, referring to the initial state before divinatory numbers, the odd number one（written as—）and the even number two（written as --）, are applied or before the yarrow stems are divided. Divination is conducted on the basis oftaiji. Third, it stands for the highest point or boundary of space.
Changes evolve from taiji, which gives rise to two primal forces of yin and yang. They in turn give birth to heaven and earth. (An Alternative Explanation of The Book of Changes)
Taiji is the overriding law of all things, as well as heaven and earth. (Classified Conversations of Master Zhu Xi)