唐期初年環繞法相宗的五種種性說法和其相關觀念發生的論爭，乃是中國佛性教理史裹最教人矚目的一章。在當時眾多論題中，「真如所緣緣種子」是最備受關注者之一。「真如所緣緣種子」觀念源出《瑜伽師地論》，論文一方面表示「一切皆有真如所緣緣」，認定真如為遍及一切眾生；另方面則把構成四種種性界別的二障形容為「畢竟」，透露出眾生種性之分殊為不可改變的設想。全本《瑜伽師地論》是在唐期初年，經由玄奘翻譯傳入中國。玄奘和其高弟窺基，受到印度瑜伽行論師護法之釋義影響，自法相宗一分眾生無佛性的觀點出發，把二障之為「畢竟」，歸因於作為成佛本因的本有清淨種子的欠缺，從而深化四種種性分別為本然不可移易的構思；又據原論以「所緣綠」稱呼真如，辯說真如要為客體的觀習對象，由是其通遍性並不能保證作為主體的眾生悉得成佛。玄奘、窺基的解說受到以如來藏思想為其教學本位之法寶的挑戰，法寶本於如來藏思想的全分眾生有佛性的立場，把「一切皆有真如所緣緣」，解釋為肯認一切眾生悉有自性清淨的理心；把二障之為「畢竟」，歸因於誹謗人、法二空，進而約謗法之重罪可以消滅，辯說二障之「畢竟」性為暫時。法寶的異釋招致以捍衛玄奘、窺基之法相宗教學為己任的慧沼的反擊。慧沼以「不平等」為理由，質疑作為法寶之釋說的核心的理心觀念，又廣引經論的說話，力證謗法非二障的本因，堅持本有無漏種子方是畢竟二障、從而亦是四種種性界別形成的依據。整體看，爭辯雙方各自依其自身教學取向，對原論之陳義，作出選擇性引申；雖然能自圓其說，卻未能教對方信服。

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 tathata¯lambanapratyaya- bı¯ja (zhenru suoyuanyuan zhongzi, true reality-objective condition-seeds). The concept was first brought up in the Yoga¯ca¯rabhu¯mi-´sa¯stra to explain liberation from rebirth. On the one hand, the ´sa¯stra admits all sentient beings possess tathata¯lambana-pratyaya-bı ¯ja as the cause of liberation; on the other hand, the ´sa¯stra affirms the existence of permanent “obstructions” (a¯varan.a) that prevent certain groups of sentient beings from ever realizing a¯varan. a. This paper attempts to examine how the ambiguity of the concept and the inconsistency in the pronouncements of the ´sa¯stra were manipulated by representative figures on both sides of the debates in favor of their respective positions.