Li Tongxuan李通玄 （635-730 or 646-740）, a contemporary of Fazang法蔵, devoted himself to reinterpreting the Gaṇḍavyūha-sūtra with the logic of indigenous Chinese thought such as the Zhouyi周易, was excluded from the orthodox genealogy of the Huayan School which was formed in the Song dynasty, and was rejected by the orthodox lineage of Dushun杜順, Zhiyan智厳, Fazang, Chengguan澄観, and Zongmi宗密. However, Li Tongxuan’s explanation of the dharmadhātu had an important influence on the construction of the dharmadhātu theory of Huayan Buddhism which unifies the Four realms of reality （si fajie 四法界） with the One true realm of reality （yizhen fajie一真法界）.
This paper systematically analyzes Li Tongxuan’s interpretation of the concept of dharmadhātu, focusing on the forty volumes of the Xin huayanjing lun 新華厳経論, and draws two conclusions. First, although Li Tongxuan’s view on the concept of dharmadhātu is based on the acceptance and inheritance of the theory of principle and phenomena of orthodox Huayan, his introduction of the concept of true wisdom provides a new direction for interpretation of the Gaṇḍavyūha-sūtra, offers a new perspective for the explanation of the dharmadhātu, and greatly enriches the content of the doctrine of dharmadhātu. Second, Li explains the concept of dharmadhātu in the context of the relationship between essence-function and principle-awareness, and asserts that the dharmadhātu is the “One true” （yizhen 一真） itself. He constructed the theoretical basis for the sansheng yuanrong 三聖円融 （perfect interfusion of the three holy ones, Vairocana, Mañjuśrī, and Samantabhadra） from the essence-function of the dharmadhātu.
