中國的華嚴宗五祖──宗密大師，依如來藏思想，對中觀與唯識進行了批評與融攝，最後並歸結中觀及唯識思想同歸一源（如來藏），這就是宗密的「合會思想」，依此宗密判定唯識教理是「密意依性說相教」，中觀則是「密意破相顯性教」，而如來藏思想則是「顯示真心即性教」。
本文旨在探討宗密以其「合會思想」，判定大乘三系的論理依據及其思惟架構，經由論證得知，宗密是將中觀的「空性」，詮釋成為如來藏的「真性」，亦即唯識相法的圓成「實性」。而對世間諸法的理解，唯識是站在「八識」的立場；中觀則是從「勝義空性」來理解；如來藏思想則是認為唯真心之外，其餘皆是妄法，且染淨諸法，無非真心所現；故大乘三系只是說法方式不同，並非教法內容有異；不同之處乃唯識「破空（無）」，中觀「破相」，而如來藏則是「直顯心性」。

From the perspective of the Tathagatagarbha school, Zongmi, the fifth patriarch of Huayan Buddhism, examined and assimilated Madhyamaka and Yogacara schools, and concluded that both came from the same origin, namely the Tathagatagarbha. Such was Zongmi’s syncretism. Therefore, Zongmi identified Yogacara as the school of diminishing delusions implicitly to cultivate the mind, and Madhyamaka as the school of diminishing discriminations implicitly to follow the middle way, and finally Tathagatagarbha as the school of directly realizing the true mind.
This paper discusses how Zongmi classified three Mahayana systems with his syncretism. Zongmi interpreted both the “emptiness” in Madhyamaka, and the “consummate nature” in Yogacara as the “true self” in Tathagatagarbha. While Yogacara examines all dharmas from the perspective of “eight consciousnesses,” Madhyamaka does this from the perspective of “ultimate emptiness.” Contrary to the above, Tathagatagarbha believes that all defiled, or non-defiled dharmas are manifestations of the true mind. Except for the true mind, all else are illusions. Therefore, three systems of Mahayana differ not in their contents, but rather in their respective approaches, where Yogacara negates nothingness, Madhyamaka denies the reality of all forms, and Tathagatagarbha directly realizes the true mind.