The mind-only thought of Huayan philosophy originates in the notion of "the three realms are mind only" taught in the Avatamsaka-Sutra, and in the concept of "the two gates of the one mind" expounded in the "Treatise on the Awakening of Faith in the Mahayana". According to the "Treatise on the Awakening of Faith", the Tathagatagarbha is the combination of the neither-arising-nor-extinguishing with the arising-and-extinguishing, both are neither one nor different, everything in the universe is the manifestation of the Tathagatagarbha. The Huayan-school chose this concept as the foundation of its teachings. When Zhiyan, Fazang, Chengguan, and Zongmi developed their own versions of mind-only teaching, they all adapted this concept from the "Awakening of Faith" as their basis. Zhiyan (602-668) distinguished the false mind from the true mind (the pure mind of the Tathagatagarbha nature), and explained the origin and transformations of all things in the universe as depending on the true mind, which therefore is the subject of deliverance, the basis of buddhahood. Fazang (643-712) emphasized the role of the "mind", too. For him, all things as well as their differences are manifested by the "mind", nothing exists independent from it. He taught that one only has to extinguish false thoughts and the discriminating workings of the mind in order to penetrate into the substance of the true mind. Chcngguan (738-839) distinguished the "corresponding mind" from the "non-corresponding mind", developed concepts about the mind-only nature of all objects, cessation of the subject-object difference in the one mind, and the Tathagatagarbha nature as intrinsic to all beings. Furthermore, he on the one hand taught that the "mind" is the ultimate origin of all things in the universe, but on the other hand he stressed that the "mind" is free from ignorance and endowed with pure knowing, and that "knowing and stillness are one". This concept of a non-abiding substance of mind endowed with enlightened knowing became one of the main characteristics of Huayan mind-only thought. Zongmi (780-841) distinguished several forms of mind, i.e. the organ (the heart), the discriminating mind, the collecting mind, and the true mind, which is also called "true mind of original enlightenment". This mind is characterized by purity, brightness, and unity of knowing and stillness. Zongmi held that "stillness" and "knowing" represent a substance-function relation, a concept obviously influenced by Chcngguan's notion that "knowing and stillness are one". However Zongmi put more emphasis on the aspect of "knowing". He held that "knowing" expressed the essence of the "mind". Furthermore, he taught that the ultimate origin of all sentient beings was the true mind of original enlightenment, and the aim of Buddhist practice was to return to this origin. This represents a further development in the theory of one mind. The mind-only thought of the Huayan-school influenced the 10(superscript th) century Fayan-school Chan-master Yongming Yanshou, as well as the theory of mind of Lu Jiuyuan (1139-1193) and Wang Shouren (1472-1528).
