The proposed lecture aims at presenting the idea of the 'Buddha-nature of the insentient' (wuqing you xing 無情有性), a basic tenet formulated by the Tiantai 天台 school of Chinese Buddhism. It explores the dimensions of the interconnectedness of the self and the surrounding environment, taking Zhanran's 湛然 (711−782) authoritative treatise, Diamond scalpel (Jin'gang bei 金剛錍; T46:1932), as a case study. First, parallel to defining key terms, the expanding dimensions of the concept of Buddha-nature (Foxing 佛性; Tathāgatagarbha) in Chinese Buddhism will be briefly presented, evolving from being understood as universally inherent in sentient beings, towards encompassing 'grasses and trees' (in Jizang's 吉藏 philosophy), and finally referring to 'tiles and stones' (Zhanran), as well. The major part of the presentation will focus on Zhanran's philosophy, and his argument that Buddha-nature cannot be understood as some sort of pure essence, locked inside the self (body and mind) of sentient beings, and separated from the surrounding environment, but it is rather an ongoing process, leading towards Buddhahood, which implies both the mind and the objects of cognition (i.e., the external environment), as experienced by the reflecting mind. Zhanran states that, no less than from the perspective of the ultimate reality, there is no real difference between the self and the world one is experiencing; this is true at the level of Buddhas and their pure lands, and sentient beings and their realms. Finally, some further implications of this concept, a theory debated but largely assimilated by the Sinicized schools of Buddhism, are contextualized as a potential foundation for modern Buddhist environmental narratives.