Summary T'ien-t'ai Chih-I advanced the theory of "evil in Buddha-nature" in Kuan-yin Hsuan-yi. This teaching was promoted to be the most important and most profound thought of T'ien-t'ai school by the scholars of T'ien-t'ai. Since the T'ien-t'ai theory of inherent evil in Buddha-nature is unique and radically deviant from the traditional concept of the nature of the Buddha (or the tathagata)，and is usually confused with the traditional theory of human-nature in China, it has incited many arguments and critiques from the scholars of other schools. In this thesis, I will inquire the implications and the significance of the T'ien-t'ai theory of inherent evil in Buddha-nature. First of all，I will deal with the traditional thoughts of the human-nature in China (Meng-Tzu，Hsun-Tzu，Yang-Hsiung) in the second chapter. Then，I will look into the Buddhistic doctrinal source of the theory of inherent evil in Buddha-nature by discussing the "teachings of Manjusri" and Ta-ch'eng chih-kuan Fa-men，etc. The third chapter will discuss the main teachings of Chih-I -- "harmonious three truths"，"three thousand worlds immanent in one moment of thought"，"mutual contrary identity"; and then try to find the possibility of emergence of the theory of evil in Buddha-nature in the main thoughts of Chih-I. The fourth chapter will elucidate the thought of "evil in Buddha-nature" in Kuan-yin Hsuan-yi. After that，I will discuss the critique，which comes from Pu-Chi to illustrate the problematik of the theory.
