One is equated with Tao—the ultimate unity of Heaven (e.g. Yang), Earth (e.g. Yin) and Man (Multitudes). Similarly, the number “one” in Chih-i’s system is the representation of the Ultimate Truth. This Ultimate Truth is absolute, inasmuch as it reveals the authentic nature of reality. Therefore, this Ultimate Truth refers to the one vehicle of Buddhahood, the ultimate goal for all living beings to strive for, which is the theme of the Lotus Sūtra. The Three Vehicles (śrāvaka, pratyekabuddha, and bodhisattva) are all unified under the Buddha-vehicle. (Page 129)