This term means one should not only have a good command of the basic rules that govern things, but also know how to deal with exceptional situations or problems in a flexible manner. It suggests that one should not just adhere to principles, but also act according to circumstances. Chang (常permanence) and bian (变change) are two opposing concepts in ancient Chinese philosophy. The nature of things that decides what they are, and their basic rules or general principles that are relatively stable are called chang (permanence); but when it comes to specific situations or ways to deal with them, they are different and change in different circumstances, thus they are called bian (change). Relative to change, permanence is what endures within change. Permanence is fundamental while change is a deviation. Therefore, one needs not only to have a good command of the basic rules and general principles of things, but also know how to apply these rules and principles in a flexible manner according to objective circumstances. The mastery of both permanence and change reflects ancient Chinese people’s perception of both generality and particularity as well as principles and flexibility. It also shows their methodology in the application of both.