Chan Buddhism as we know it today can perhaps be traceable to what is known as the Hongzhou school, founded by Mazu Daoyi. Although it was Huineng who represented an important turn in the development of Chan with his iconoclastic approach to enlightenment as sudden rather than gradual, it was in Huineng’s successor, Mazu, where we saw its complete radicalization. Specifically, Mazu introduced a radicalized approach of collapsing substance (體 ti) and function (用 yong), as well as principle (理 li) and phenomena (事 shi), into a complete overlap. As a result of this radicalization, the Hongzhou lineage received some strong criticisms, the most important of which was possibly by Guifeng Zongmi, of the Heze lineage. Zongmi criticized Mazu for his supposed antinomianism, claiming that Mazu’s approach completely stunts moral and religious cultivation. Due to their commitment to “suchness” rather than deliberate theory, however, Hongzhou never bothered to answer Zongmi’s critique. As such, it is the goal of this article to utilize Guo Xiang’s philosophy as a tool to understand the implicit Hongzhou response to Zongmi. As I shall demonstrate, his philosophical enterprise shares the same ontology of absolute oblivion which Hongzhou was also predicated upon and is, therefore, a possible alternative to understanding what could have been the Hongzhou response to the alleged antinomianism.