The four-character statement “Yi yi ni zhi” 以意逆志 by Mencius on how to interpret the Book of Poetry has won praise from critics of all persuasions for nearly a millennium. How could this Mencian statement become a credo for so many different and often mutually opposed interpretive traditions? The extraordinary “versatility” of the Mencian statement, this article suggests, has much to do with the rich inherent ambiguity of uninflected classical Chinese. By adroitly exploiting the ambiguities of the words yi 意, ni 逆, and zhi 志 as well as its syntax, traditional Chinese critics continually reinterpreted the Mencian statement in a way that justified their novel interpretive approaches. So, by investigating the continual reinterpretation of the Mencian statement, this article maps out the rise of diverse interpretive approaches from pre-Han times through the Qing. It also discovers two distinctive thrusts of these approaches and sheds light on the underlying dynamic unity of the Chinese interpretive tradition.