This concept means generally applicable principles and tangible concrete objects, which are an important pair of concepts in ancient Chinese philosophy. Dao is invisible, concealed and metaphysical, while objects are tangible, visible and physical. The former represents unity of things, while the latter demonstrates diversity of things. However, the two are not diametrically opposed to each other. Rather, they are inherently in unity in that the former is the abstraction of the latter, while the latter is the concrete manifestation of the former, and the two have a relationship of dialectical unity.