Chih-i expresses his conception of the ultimate truth of phenomenal entities as the simultaneous affirmation of “three truths”: That which originates dependent on causes and conditions is (1) empty (k’ung), (2) provisionally (i.e., dependently) existent (chia), and (3) the middle way (chung). The simultaneous affirmation of emptiness and dependent existence is obviously in accord with Mādhyamika philosophy. The assertion of the third, middle truth, however, has reinforced the view that Chih-i introduces to his conception of the ultimate truth notions from the tathāgata-garbha tradition. While some interpreters believe that the third, middle, truth is nothing more than the explicit affirmation of the identity of the truth of emptiness and the truth of provisional existence, others hold that the middle truth is a reference to the real, absolute pure mind of the tathāgata-garbha tradition.
Indeed, Chih-i’s characterizations of the ultimate truth are ambiguous and often appear to affirm monistic conceptions like that found in the Tathāgata-garbha sutras. In addition to defining ultimate truth as the simultaneous affirmation of emptiness and dependent existence, he defines it on some occasions as the negation of both emptiness and dependent existence and on others as the simultaneous affirmation and negation of emptiness and dependent existence. The impression created by these descriptions of an absolute reality transcending the realm of empty, dependently originating phenomena is further reinforced by Chih-i’s consistent use of the term tathāgata-garbha to refer to the ultimate truth.
Nonetheless, the central importance in Chih-i’s thought of the identity of all phenomena with ultimate truth militates against the idea that Chih-i understands the ultimate truth as a pure mind. When ultimate truth is conceived as a pure consciousness, in itself devoid of conceptuality and its objects, there is a fundamental dichotomy between the ultimate truth and the phenomenal realm. Even when, as in the Hua-yen tradition, the pure consciousness is understood as the ground for the appearance of the phenomenal realm, a true oneness of the phenomena and ultimate truth is not obtained; the phenomena are one with ultimate truth only insofar as phenomenal particularity is transcended and one discovers the unitary pure consciousness within all.
A Buddhist Kaleidoscope; Susan Mattis, Chih-i and the Subtle Dharma of the Lotus Sutra: Emptiness or Buddha-nature?, Page 253