In Tiantai Buddhism, the concept of Buddha nature plays a central role in understanding the ultimate goal of spiritual practice. Buddha nature refers to the innate potential for enlightenment that exists within all beings. According to Tiantai, this Buddha nature is not something that needs to be acquired or attained, but rather it is already present within each individual.

Tiantai views Buddha nature as the fundamental nature of all things, including both sentient and non-sentient beings. This means that all beings, regardless of their current state, possess the potential to become Buddhas. This concept is in line with the Mahayana belief in the universality of Buddha nature, which states that all beings have the capacity to attain enlightenment.

Tiantai also emphasizes the idea of the "One Vehicle" or "One Dharma," which means that all Buddhist teachings are ultimately leading to the same goal of awakening. This includes the Lotus Sutra, which is considered the most essential teaching in Tiantai Buddhism. The Lotus Sutra is seen as the ultimate expression of the Buddha's teachings, and it is believed to contain the complete understanding of Buddha nature.

Tiantai teaches that the Lotus Sutra is the key to unlocking one's Buddha nature. By studying and practicing the teachings of the Lotus Sutra, one can awaken to their innate potential for enlightenment. This is because the Lotus Sutra reveals the ultimate truth of the universe and helps individuals realize their true nature.

Furthermore, Tiantai also emphasizes the concept of the "three truths" or "threefold truth." This refers to the idea that all phenomena are simultaneously empty, temporary, and interdependent. This understanding of the three truths is crucial in realizing one's Buddha nature. By understanding the emptiness of all things, one can see that their Buddha nature is not separate from the ultimate truth of the universe.

Overall, Tiantai views Buddha nature as the essential nature of all beings and the ultimate goal of spiritual practice. Through the study and practice of the Lotus Sutra and the understanding of the three truths, one can awaken to their Buddha nature and attain enlightenment. This concept highlights the inclusivity and universality of Tiantai Buddhism, as it teaches that all beings have the potential to become Buddhas and attain ultimate liberation.