Hua-yen Buddhism is generally considered as the most theoretical and systematic presentation of Buddhist ideas among the various Buddhist schools that appeared in China during the Sui-T'ang period (589-900 A.D.). Furthermore, its philosophico-religious teachings played a significant role in the religious history of East Asia. In spite of such an importance, very little is known about Hua-yen Buddhism in the Western world. This thesis, therefore, attempts to achieve a proper understanding of Hua-yen Buddhism through an extensive investigation of its central doctrine of dharmadhātu(fa-chieh) as it occurs in the writings of the patriarchs of the Hua-yen school. Part One, as a background study, examines first of all the etymological and contextual meaning of the term dharmadhātu. It also surveys the Avatamsaka-sūtra(Hua-yen ching), the canonical scripture from which the Hua-yen school derived the idea of dharmadhātu as the central theme for teaching and meditation. In addition, it discusses the background and development of the Hua-yen school. In Part Two, the main body of the study, the dharmadhātu doctrine of the Hua-yen school is examined in terms of its development. The basic writings of its five patriarchs and their ideas concerning "the dharmadhātu are chronologically and systematically analyzed in detail. It is demonstrated that the dharmadhātu doctrine can be said to have been, by and large, founded by Tu-shun, formulated by Chih-yen, systematized by Fa-tsang, and elucidated by Ch'eng-kuan and Tsung-mi. Part Three, the concluding part, embarks upon an inquiry into the significance of the Hua-yen dharmadhātu doctrine. It is argued that the dharmadhātu doctrine is not "a pointless exposition of empty words," as characterized by some outside critics, but that it contains solid "philosophical," "religious," and "historical" significance within it. First, it is clarified that the dharmadhātu doctrine is meant to lead man toward an insight into the interrelatedness, that is, the "mutual identification" and "interpenetration," of all the dharmas — an insight which liberates him from all kinds of rigid philosophical preconceptions and dogmatism concerning reality. Second, it is also discovered that the dharmadhātu doctrine of mutual identification and interpenetration is relevant to the formulation of the religious conviction of the "instantaneous attainment of Buddhahood" upheld by the Hua-yen school. Finally, it is verified through concrete evidence that the dharmadhātu doctrine exerted a significant influence on the religious thought of China, especially on the Ch'an(Zen) and the T'ien- t'ai traditions, Taoism, and Neo-Confucianism.
