In the past I’ve expressed puzzlement at the prediction that future Buddhas will divide the One Vehicle into three in order to save sentient beings.

Why bother? Because even though “the world in which he appears will not be an evil one” the causes and conditions that prompted the Buddha’s provisional teachings will still be present. This significantly alters the meaning of the Mahāyāna.

This is reflected in Jan Nattier’s discussion of The Inquiry of Ugra. As Nattier explains:

Far from describing the Mahāyāna as a form of protest against those pursuing the traditional path to Arhatship, the Ugra urges its audience to maintain harmony within the Buddhist community by honoring one’s Śrāvaka coreligionists. There is, in sum, not a shred of evidence that the Ugra’s authors considered the Śrāvaka path illegitimate–far from it, for they remind the bodhisattva that when he becomes a Buddha, he will lead a community of Śrāvakas himself.

A Few Good Men, p194

In The Inquiry of Ugra, the Buddha says:

“O Eminent Householder, how should the householder bodhisattva go to the Sangha for refuge? O Eminent Householder, as to the householder bodhisattva going to the Sangha for refuge, if he sees monks who are stream-enterers, or once-returners, or non-returners, or Arhats, or ordinary persons (pṛthagjana), who are members of the Śrāvaka Vehicle, the Pratyekabuddha Vehicle, or the Great Vehicle, with reverence and respect toward them he exerts himself to stand up, speaks to them pleasantly, and treats them with propriety. Showing reverence toward those he meets with and encounters, he bears in mind the thought ‘When I have awakened to Supreme Perfect Enlightenment, I will teach the Dharma which brings about [in others] the qualities of a Śrāvaka or a Pratyekabuddha in just this way.’ Thus having reverence and respect for them, he does not cause them any trouble. That is how a householder bodhisattva goes to the Sangha for refuge.

A Few Good Men, p218-219

I agree with Nattier’s declaration that the Mahāyāna can be seen as a synonym of the “bodhisattva path,” but she misses how The Inquiry of Ugra sets up the Bodhisattva and the Mahāyāna as a distinct and superior path. Consider this description of the Three Refuges for Bodhisattvas:

“And again, O Eminent Householder, if a householder bodhisattva has four things, he is one who ‘goes to the Buddha for refuge.’ What are the four? (l) he does not abandon the spirit of enlightenment; (2) he does not break his promise; (3) he does not forsake great compassion; and (4) he does not concern himself with the other vehicles. O Eminent Householder, if a householder bodhisattva has these four things, he is one who ‘goes to the Buddha for refuge.’

“And again, O Eminent Householder, if a householder bodhisattva has four things, he is one who ‘goes to the Dharma for refuge.’ What are the four? (l) he relies on and associates with those people who are preachers of the Dharma, and having revered and done homage to them, he listens to the Dharma; (2) having heard the Dharma, he thoroughly reflects upon it; (3) just as he has heard and absorbed it himself, he teaches and explains those Dharmas to others; and (4) he transforms that root-of-goodness which has sprung from his gift of the Dharma into Supreme Perfect Enlightenment. O Eminent Householder, the householder bodhisattva who has these four things may be said to be ‘going to the Dharma for refuge.’

“And again, O Eminent Householder, if a householder bodhisattva has four things, he may be said to be one who ‘goes to the Sangha for refuge.’ What are the four? (l) those who have [not yet] definitively entered into the Śrāvaka Vehicle he should lead to the spirit of Omniscience; (2) those who are drawn to material things he causes to be drawn to the Dharma; (3) he relies on the irreversible bodhisattva Sangha, not on the Sangha of the Śrāvakas; and (4) he strives for the good qualities of the Śrāvakas, but does not delight in their form of liberation. O Eminent Householder, if a householder bodhisattva has these four things, he may be said to be ‘going to the Sangha for refuge.’

A Few Good Men, p219-222