 By contrast, all serious Mahāyānists take the bodhisattva vow, promising to become Buddhas in order to help all beings. Indeed, some scholars have concluded that the Mahāyāna movement began within the framework of early Buddhism as a group of practitioners holding the same doctrines and embracing the same rituals as their fellow Buddhists, and distinguished only by their common choice to follow the path to Buddhahood. However, over time, many other differences evolved. In particular, mature Mahāyāna traditions tend to hold that those who have become Buddhas, even after they die, continue to manifest in various forms and in various parts of cyclic existence in order to carry on the work of benefiting beings. They will remain in cyclic existence until all sentient beings have reached liberation.