Jingxi Zhanran, the ninth patriarch of the Tiantai School of Chinese Buddhism, is well-known for advocating the doctrine of "the Buddhanature of insentient beings." By raising the question about subjectivity, this paper examines Zhanran's criticism of the notion that Buddhahood has a substantial nature which only sentient beings can embrace. On the basis of his critique on the illusory thoughts in relation to the substance of Buddha-nature, Zhanran, in contrast with the common belief harboured by most of the Buddhist scholars of his time, articulates that not only sentient beings but also insentient ones, e.g., flora, mountains, rivers, and manmade objects, have Buddha-nature. This paper ultimately argues that Zhanran proposes the Buddhanature of insentient beings not with the aim of diminishing the nobility and subjective initiative of tathāgata-garbha, but with a view to transcending the duality between selfness and otherness, and subjectivity and objectivity. Nevertheless, it is also noteworthy that Zhanran's advocacy of insentience's Buddha-nature should not be viewed as equivalent to the proposition that all insentient beings such as trees, grass and flowers are allowed to attain Buddhahood.