Fu-san Hsien-i (Covering the three and revealing the one) is the function related to the Subtlety of Positions. This is spoken of by Chih-i in terms of various expedient methods that are skillfully employed by the Buddha. Instead of destroying the Three Vehicles, the Buddha covers them in order to reveal the One Vehicle, which is for the purpose of creating more possibilities of transforming living beings. Covering the three instead of destroying them leaves the possibility to use them once again, should the causes and conditions rise later on. Since the Buddha’s skillful employment of various expedient methods can result in different levels of attainment, this function is associated with the Subtlety of Positions. (Vol. 2, Page 446)