 Zhu Xi’s penchant for thinking in polarities, li and qi, in particular, has continued to stir critics to regard him as a dualist who used two fundamental concepts to explain reality. For his part, any viable account of the complexity of phenomena must involve two or more facets in order to register their complexity, variety, and changes. Zhu generalized the organic understanding of li and qi implied in Zhou Dunyi’s Explanation under a principle of complementarity, inspired by Cheng Hao’s observation that all things have their complement (discussed in the next section). At first, Zhu thought this principle only governed qi phenomena as patterned by li, but eventually he admitted that not only were yin and yang paradigmatic polar complements but that the supreme polarity (taiji) complemented the yin-yang polarity, and inferred that li and qi, as the references of taiji and yin-yang, respectively, too had to be complements. This meant that li and qi were functionally on a par and mutually implicative. Zhu still felt the need to prioritize li ontologically and ethically, however, for the reason that li underwrites both the possibility of qi ordering (to yield a world and phenomena) and the possibility of moral feelings and norms (to yield ethics and a system of rites). Treating li and qi as full ontological complements would quite possibly entail a Daoist conception of nature as pure spontaneity and ethics as just perspectival while prioritizing qi over li would be inadequate for understanding the world and phenomenal orders, and reduce ethics to the received norms.