How can Chih-i’s philosophy assume “perfect and harmonizing” (Yüan-jung)? Based on our study of the work Hsüan-i (Profound Meaning of the Lotus Sūtra), we would like to propose that it is due to several characteristics of the Ultimate Truth demonstrated by Chih-i that corresponds to his own philosophy that his philosophy as perfect harmonization is established.

First, Chih-i associates the Ultimate Truth with the One Buddha-vehicle (that is advocated in the Lotus Sūtra). This is because the One Buddha vehicle stands out to be supreme in position with which one can attain Buddhahood. Its superiority legitimatizes itself to be the unifying force that embraces all different doctrines in Buddhism and converges all the other Three Vehicles (śrāvaka, pratyekabuddha, and bodhisattva). Apparently, speaking in terms of the Buddha-vehicle, the Ultimate Truth bears all-embracing nature, and functions to reconcile differences.

Second, the Ultimate Truth is linked to the state of subtlety, seeing that it consists of three aspects (substance, position, and function), and the relationship between one and three is inconceivable. Chih-i defines this subtle state of inconceivability as neither the same nor different, with which the nature of flexibility of the Ultimate Truth is emphasized: “The one aspect that is discussed contains the three aspects; the three aspects that are discussed are actually one aspect. These aspects are not different from each other, neither are they besides one another nor are they the same. Therefore, they are called ‘subtle’.”

Third, considering that the Ultimate Truth is represented by the Buddha-vehicle, Chih-i regards the realization of the Ultimate Truth as the state of Buddhahood. This ultimate state is vehemently emphasized by Chih-i to be quiescent and illuminating. For instance, in his definition of the Subtlety of the Original Empathy and Response, Chih-i states that the Buddha abides at the state of quiescence and is able to illuminate sentient beings by responding to them in order to activate their inherent wisdom. Chih-i’s focus on the aspect of illumination unravels dynamic and functional nature of the Ultimate Truth.

Fourth, the Ultimate Truth is spoken of by Chih-i in terms of the Buddha-nature that is originally possessed by all sentient beings. The Buddha-nature as the Ultimate Truth indicates that Buddhahood can be universally attained by all beings, and that Buddhahood is the ultimate goal for religious salvation, whereas it does not exclude any being. On the other hand, the concept of Buddha-nature draws a complete scheme of religious path to liberation, for it includes the cause and effect of Buddhahood. The Buddha-nature that is embedded in all beings denotes the potentiality of beings as the cause for attaining Buddhahood. The manifestation of the Buddha-nature indicates the attainment of Buddhahood as the effect. Thus, by revealing universal liberation of all beings, the Buddha-nature as the Ultimate Truth is designated the feature of non-exclusiveness (i.e., comprehensiveness). The Buddha-nature as the Ultimate Truth that includes the cause for Buddhahood in the beginning and the effect of Buddhahood at the end of religious path formulates a feature of completeness and perfection. (Page 36-37)