＂Prajñā＂ is a special Buddhist wisdom, namely a sublime wisdom that guides living beings towards liberation from the sufferings of their passions and attainment of a state of physical and mental tranquility. This wisdom is mainly articulated in theories about the emptiness of all phenomena and the two truths of the absolute and the relative, a comparatively complete system of thought. In other words, emptiness of everything that is conditioned by causes and the theory of two truths are important concepts of the prajñā system of thought. This paper discusses the concepts of emptiness and two truths in the writings of monks who according to the Xianshou chuandeng lu and the Xianshou zongsheng belonged to the Huayan school. First, the paper explains how Jingyuan (1011-1088) understood form and emptiness and the two truths. He expounded the meaning of ＂form is emptiness, emptiness is form＂, and explained the relationship of absolute truth and relative truth as mutually excluding each other yet at the same time non-dualistic. Next, Zunshi's (1041-1103) concept of the two truths is explained. He combined each of the concepts of ＂form＂ and ＂nature＂ with the relative truth, and declared ＂four phrases of relative truth＂; then he combined ＂form＂ and ＂nature＂ with absolute truth, resulting in the ＂four phrases of absolute truth＂, and declared the wonderful meaning of neither existence nor non-existence of absolute truth and relative truth. Next, Wencai's (1241-1302) concept of emptiness is discussed. He maintained that all corporeal dharmas that originate from causes have no permanent reality, they are like a dream, which is void of any substance. He also thought that ＂form＂ and ＂emptiness＂ are neither identical nor separated, neither one nor different. Finally, the paper explains Purui's (dates unknown) understanding of the two truths. He thought that the ＂true suchness of mind＂ of the Dasheng qixin lun represents the absolute truth, and that the ＂arising and perishing aspect of mind＂ represents the relative truth, and declared that because of the interpenetration of ＂real＂ and ＂unreal＂, they do not impede each other, the absolute truth and relative truth are complementing, not opposing each other. The conclusion points out that during the Song and Yuan dynasties monks belonging to the Huayan school, especially Jingyuan and Wencai, mainly followed the tradition of Zhaolun and further expounded its meaning, clarifiying its characteristic prajñā thought. Jingyuan, Zunshi, and Purui explained the concept of the two truths, clarified the characteristics of the two truths, and thereby enriched the Huayan school thought of that era.
