Here, a central tenet of Mahāyāna Buddhism, the doctrine of expedient means, is defended in light of the Quinian doctrine of ontological commitment. The need for such a doctrine arises because of significant disparities between Mahāyāna Buddhist teachings and those of Theravāda Buddhism, which are historically prior. In particular, the Lotus Sūtra deploys the doctrine to explain why the Buddha had taught multiple vehicles (ways to enlightenment) when there is in fact only one, the Buddha’s own way. It is argued here (1) that at least some Buddhist apologetics have been directed toward defending the Buddha against an accusation that he lied; (2) that the Lotus Sūtra does not deny that the Buddha lied, but rather that he spoke a falsehood; and (3) that although it is unclear whether the Buddha can be defended against an accusation of lying, it is provable that he spoke no falsehood in preaching multiple vehicles. The proof depends on the logical regimentation of Mahāyāna and Theravāda views as formal languages with disparate discriminative resources. On this basis strict limits can be derived for the number of vehicles to which the users of each language are ontologically committed. The upshot is that the Mahāyāna Buddhist can claim that her theory supersedes the earlier teachings without having to deny the truth of those teachings; they were true because they were assertible in the theory of enlightenment in which they were originally presented.