 Most Confucians in the Song-Ming period believed that all phenomenal things and events are constituted of qi, a kind of vital, energetic material. But many doubted that qi alone could account for everything of significance about the phenomenal world. The world has a certain unity and order that they saw as highly valuable, evident in things such as the natural behaviors of plants and animals, and the way that seasons work cooperatively with living things (and with one another) to sustain and reproduce life. And human beings have certain capacities to understand and contribute to the order and unity of things, capacities that seem to be part of our natural endowment. Many Neo-Confucians thought that some further explanatory principle or ground was needed to account for this order, unity, and the natural capacities that help us make sense of them, and for this they appealed to the notion of Pattern (li).