 Zhu conceptualized nature and natural phenomena in terms of li (pattern, patterning) and gewu (the investigation of things), qi (primal vapor), yin-yang, wuxing (five phases), shu (number, probability, ratio), xiang (images); figures from the Book of Changes), ghosts and spirits (gui-shen), heaven and the sage (tian-shengren), stimulus-response (ganying), and transformation and change (bianhua). In this context, it was important to treat li matter-of-factly as the intrinsic patterning of things and events. While the li involved with the identities of things are those facets of intrinsic patterning that pertain to their basic interactive propensities and functions, the li of a concrete thing form “a gestalt totality” (Kim 2000), nearly as complex as the thing itself. Thus, whereas scholars tend to take Zhu’s assertion that “for a certain (kind of) thing to exist, there first must be that li” or “there must be this li for there to be that (kind of) thing” as indicative of a metaphysical principle of sufficient reason, in this context li simply affirm that things of identifiable kinds bear identifying patterns (xing) that make them what they are and interact as they do. Li indicate reference points for identities of things that influence their typical patterns of interaction with other things. Li thus conceived do not amount to principles of explanation and are more involved with definition, so references to the li of phenomena do not add anything cognitive or  scientific.[16]  At times, Zhu did present the idea of investigating things in chapter 5 of the Great Learning (Daxue) as involving a step-by-step approach, with an eye to discerning ever higher levels of commonality among the myriad li (patterns), aiming at an ultimate comprehension of the most basic form of pattern, taiji (supreme polarity). Although this approach lacks the rigor of a logical categorical system, when viewed together with Zhu’s comments on Zhou Dunyi’s Diagram of the Supreme Polarity (Taiji tu), it is suggestive for viewing phenomena and forms in a developmental, almost evolutionary context. As Needham comments: