The Mahaparinirvana Sutra is an important Mahayana sutra, which advocates the eternity of the Tathagata, the universal Buddha nature in all sentient beings, and the Buddhahood of the icchantika, etc. This sutra belongs to one of the three main doctrinal systems of Indian Buddhist thought -- Tathagatagarbha thought. The Tathagatagarbha thought that emphasizes the inherent and universal pure mind emerged around the third century，and the Mahaparinirvana Sutra belongs to the second period of the development of Tathagatagarbha thought. It's most controversial doctrines lies on its associating Tathagatagarbha with atman，and the enlightenability of the icchantika.
This article is divided into three parts. The first part deals with different versions of the sutra. Since the original Sanskrit text was lost，this part focuses on the textual study of the Chinese translations. The second part examines in detail the main teaching of the sutra：the eternity of the Tathagata, the nature of Nirvana, the universal Buddhahood of all sentient beings. The meaning of the icchantika and the possibility of their enlightenment are thoroughly examined.
The third part discusses the theory of Buddha nature from five viewpoints： (1) From "two causes" and "three causes"; (2) From the theory of causality; (3) From the "ultimate meaning of emptiness"; (4) From the existence of virtues and voidness of afflictions; (5) From the definite and indefinite nature of all dharmas.
