The “Nirvāṇa by the two vehicles” refers to the enlightenment achieved by Sravakas and Pratyekabuddhas under the guidance of the Lesser Vehicle. Because students of the Lesser Vehicle looked upon the world negatively (as something from which to escape), they eventually refused to continue the dangerous and tiresome journey through life. The enlightenment which they attained could be described as “reducing the body to ashes and the mind to annihilation in the great void.” But this, said the Buddha, is only an expedient along the journey. It is meant only to keep people from getting attached to physical or mental objects.