 The world is characterized by ceaseless change and transformation, which at first glance may appear haphazard; but as the Yijing has shown, change conforms to basic principles—not static metaphysical “forms,” but dynamic modes of operation—that can be described generally in terms of the interplay between the yin and yang vital forces. In this sense, the Laozi remarks that human beings are “modeled” after heaven and earth, and ultimately, after Dao (commentary to Laozi 25).