 The key to understanding (and thus also knowing how to employ) all forms of human knowledge is to understand the nature and pattern of the root in which these myriad ways are grounded. The same patterns are manifest not only in different areas of human knowledge, subjects, people, customs, languages, etc., but also in the rest of the world. One of the key features of Han syncretic thought and “correlative cosmology” is the linking of the general structure of humanity and the cosmos (tian), such that the very same patterns govern both. This insight is behind much of what I have called the “naturalistic shift” of the Han, and the origins of much of early Chinese science in the Han period. Some examples of this are the development of the medical tradition, found in early texts such as the Huangdi Neijing, and the systematization of astronomy, geography, calendrics, and mathematics. The earliest texts in these areas date to the Han period, and we find general discussions of these areas in texts such as Huainanzi that attempt to organize all human knowledge. Thus we have chapters on astronomy (Tianwen, ch. 3), calendrics and seasons (Shize, ch. 5), and other areas of natural science.