The debates in the early Tang (late seventh and early eighth centuries) over whether all sentient beings can attain Buddhahood form an important chapter in the history of the development of the Buddha-nature teaching in China. One of the most central points of conflict occurs with the interpretation of the concept tathatālambana-pratyaya-bīja (zhenru suoyuanyuan zhongzi, true reality-objective condition-seeds). The concept was first brought up in the Yogācārabhūmi-śāstra to explain liberation from rebirth. On the one hand, the śātra admits all sentient beings possess tathatālambana-pratyaya-bīja as the cause of liberation; on the other hand, the śāstra affirms the existence of permanent "obstructions" (āvarna) that prevent certain groups of sentient beings from ever realizing āvarana. This paper attempts to examine how the ambiguity of the concept and the inconsistency in the pronouncements of the śāstra were manipulated by representative figures on both sides of the debates in favor of their respective positions.