Chih-i offers an explanation for his preference of the position of the Perfect Teaching over those of the other three teachings in terms of the Relative and the Ultimate. The relative teachings contain two characteristics. First, they are not upright rivers and are winding and roundabout, considering that the Buddha did not directly express his true intention of guiding beings to attain Buddhahood in relative teachings. Second, the relative teachings serve to suit the dispositions of sentient beings (Sui-ch’ing) like all forests that must have trees. By means of presenting the Three Vehicles (śrāvaka, pratyekabuddha, and bodhisattva), the Buddha uses the relative teaching to mature sentient beings so that they will be able to eventually receive the Perfect Teaching, and enter the One Buddha-vehicle. Obviously, the relative positions, which are represented by three kinds of herbal grass and two kinds of tree, are not ultimate, and have to be abolished. The ultimate positions, which are represented by the Perfect Teaching, are analogous with “the great river [named] Golden Sand that flows straight into the Western Sea” and are analogous with “all golden and silver trees that are part of precious forest.” Since these positions are not winding (i.e., entailing no expedient purpose), but straightforward (i.e., direct attainment of the Ultimate Truth), they are not to be abolished. In addition, from the point of view of integrating the three relative teachings (i.e., Tripiṭaka, Common and Separate) with the one ultimate teaching (i.e., Perfect Teaching), positions of the former teachings should be abolished, and positions of the latter teaching should not be abolished. In other words, since the One Vehicle of Buddhahood is the result of an integration of the Three Vehicles, these three no longer need to exist, but this One Buddha-vehicle is necessary to remain. (Vol. 2, Page 228)