Why did the Buddha have to take the circuitous route of three vehicles in order to lead beings to the One Vehicle? Tao-sheng offers as answer the inequality of innate intellectual faculties in individuals. The idea is Tao-sheng’s elaboration of what is loosely suggested in the sūtra. It is further reinforced by his notion of an innate triggering mechanism for the enlightenment process. This in turn gives rise to the concept of “expediency in means” (upāya), which receives Tao-sheng’s special attention and articulation with the help of the Chinese term “exigency” (ch’ūan): The limited capacities of sentient beings forced the Buddha to invent a device that would tempt them on to the path to enlightenment; hence, the figurative nature of the multiple vehicles as opposed to the literality of the One Vehicle.

How the three vehicles are related to the One Vehicle, however, is a complicated matter. Although Tao-sheng relates essentially what is stated or suggested in the sūtra, he sounds somewhat ambivalent with respect to whether the vehicles have a negative or positive value. Three vehicles, being of exigent and temporary value, are identified as false, whereas the One is identified with what is real. Nonetheless, whereas the three or two are false, and thus antithetical to the One or Greater Vehicle, they are ultimately subsumed by the One and cannot properly be thought of apart from this synthesis with the One. One thus may call it a dialectical relationship. The process is best expressed in the word miao (“mysterious” or “wondrous”).

This interpretation has the mark of Tao-sheng’s own philosophical speculation. The sūtra has this to say: “the Buddhas, by resort to the power of expedient devices, divide the One Buddha Vehicle and speak of three.” It thus seems to view the three vehicles positively. This is, however, a liberal rendering by Kumārajīva of the original text, which has no word for three. The sūtra does not mention falsehood, as it only refers to the way the Buddha guides beings through the enlightenment process rather than to the device actually used. As the Buddha states in Chapter 3: “Śāriputra, just as that great man, first having enticed his children with three carriages and then having given them only one great carriage . . . is yet not guilty of falsehood, though he first preached the three vehicles in order to entice beings, then conveyed them to deliverance by resort to only the One Great Vehicle.”