In the Profound Meaning of the Lotus Sutra, Chih-i reminds his audience that the “mind” in no way differs from all other dharmas and is singled out as the object of contemplation only because it is closest to us. (p.197)

Every dharma, contemplated in its ultimate truth, reveals itself as pervading all phenomena. Most significantly, the ordinary moment of consciousness encompasses all dharmas: “All one can say is that the mind is all dharmas and that all dharmas are the mind.” We are now in a better position to understand how the image of Śākyamuni in the Lotus Sutra represents the ultimate truth of the phenomenal realm, the Buddha-nature. From Chih-i’s standpoint, the depiction of the all-pervading Śākyamuni does not figure a “pure” consciousness that is devoid of conceptuality and its objects and simultaneously the ground of phenomenal existence; it is rather an image of the “true aspect” of the phenomena themselves, the ordinary dharmas that are at once empty and provisionally existent, each encompassing the totality and therefore both “one” and “many.” This ultimate truth of the phenomenal realm is the “Middle Way” that Chih-i refers to as the resplendent realm of the Buddha which is “eternal, blissful, selfhood and pure.” The ultimate truth may be identified as the cause of Buddhahood or the Buddha-nature (tathāgata-garbha) because it is the identity of one’s own mind with this truth which makes the realization of the truth and the attainment of Buddhahood possible. However, it must be stressed that the Buddha-nature for Chih-i is not the transcendent pure mind of the Tathāgata-garbha sutras, but simply the “true aspect” of the moment of ordinary consciousness and of all phenomena.
A Buddhist Kaleidoscope; Susan Mattis, Chih-i and the Subtle Dharma of the Lotus Sutra: Emptiness or Buddha-nature?, Page 255-256