 Before we go on, a brief explanation of Principle (理) and Vital Force (氣) is in order. First, Principle refers to the universal order of the world and, for this reason, it is the intangible and abstract yet active and dynamic source of all things. It is not only the principle of being of all things in the world but also their normative source, i.e., the source of good in the world. Thus, Principle is good intrinsically yet also transcendentally, going well beyond the confines of the manifested, phenomenal world. What is more, human nature is none other than this very same Principle concretely exemplified in humans. So, in this respect, human nature is innately good. A person has a heart/mind (sim, C. xin 心) whose nature (性) is endowed by Heaven. Since human nature is nothing other than Principle, which is in the heart/mind of a person, the heart/mind must innately point to Principle. Note that Principle itself does not move but it sets the limits on what can move in the phenomenal world. This is because Principle itself is the organizing source of reality that, while not visible, provides the structure and pattern for all phenomena. When the fullness of Principle as the fountainhead of all beings is brought to relief, Principle is called “Supreme Ultimate (t’aegŭk, C. taiji 太極)”. Supreme Ultimate thus refers to the ultimate metaphysical ground of the development of things in the world, which it generates by way of its polarity (i.e., yin and yang forces).