The debate turns in verses 40-56 to the question of whether the Mahāyāna sūtras and the teaching of emptiness they convey is authentic and whether it is necessary for attaining liberation. The hīnayānist states, “Liberation comes from understanding the [Four Noble] Truths,” and then asks, “What is the point of understanding emptiness?” Śāntideva appeals to the testimony of the Mahāyāna sūtras, saying, “The reason is that scripture states that there is no awakening without this path.” The hīnayānist, however, does not accept the Mahāyāna sūtras as canonical and asks, “Surely Mahāyāna scripture is not established?” Śāntideva replies, “In what way is your scripture established?” The hīnayānist says, “Because it is established for both of us.” In other words, all Buddhists accept the pre-Mahāyāna sūtras as canonical. Śāntideva points out that “It was not established for you at first! Apply your criteria for the acceptance of it to Mahāyāna scripture also. If something is accepted by two different parties even texts such as the Vedas would be true. If your objection is that Mahāyāna scripture is controversial, reject your own scripture since it is contested by non-Buddhists, and any part in that scripture contested by your own people or others.” The point here is that it is not the number of people who agree or disagree that something is authentic, the criteria is the validity and efficacy of what is taught.

Śāntideva then criticizes the arhats, saying that because they do not contemplate and realize emptiness they are still deluded.

“The dispensation is rooted in the monkhood and the monkhood itself is imperfectly established. Even the enlightenment of those whose minds grasp onto entities is imperfectly established. If your objection is that liberation results from the destruction of the defilements, then it should happen immediately afterwards. Yet one can see the power over them even of undefiled action. If you put forward the argument that they have no craving leading to grasping, our response is: Even if their craving is undefiled, does it not exist as delusion? Feeling causes craving, and they do have feeling. A mind which has objects will get stuck on one or another. Without emptiness a mind is fettered and arises again, as in the meditative attainment of non-perception. Therefore one should meditate on emptiness.” (IX.44-48)

He says this because the arhats are recorded as still being under the power of old habits, and even though they are free of the obstacle of the defilements of greed, hatred, and more obvious forms of delusion by realizing no-self, they have not yet broken through the obstacle to knowledge (or the obstacle of clinging to lesser knowledge) by realizing emptiness. Therefore they still have not freed themselves of fundamental ignorance and still have attachment for nirvana and aversion for samsara.

He goes on to say:

“You accept that whatever text might be in accordance with the discourses was spoken by the Buddha. So why are the Mahāyāna scriptures not accepted as equal in value to your own discourses? If the whole is faulted because one part is not accepted, why not treat the lot as spoken by the Conqueror because a single part is the same as in the discourses? Who will bar acceptance of the teaching over which those led by Mahākāśyapa hesitated, simply because you do not understand it?” (IX.49-51)

Śāntideva is pointing out that it doesn’t make sense to accept or reject everything simply because you accept or reject one part. It also doesn’t make sense to reject something simply because you don’t understand it at first, as Mahākāśyapa and the other arhats admitted to doing in the Lotus Sūtra.

In conclusion he says:

“Remaining in cyclic existence for the benefit of those suffering through delusion is achieved through freedom from the two extremes, attachment to nirvana and fear of samsara. This is the fruit of emptiness. So, that being the case, there is no valid objection to the emptiness position. Therefore, emptiness should be meditated upon without reservation. Since emptiness is the countermeasure to the darkness of the obstacle to knowledge and the obstacle of the defilements, how is it that one who desires omniscience does not make haste to meditate upon it? Granted that something which causes suffering causes fear – but emptiness allays suffering. So why does it cause fear? Granted, too, fear may come from any quarter whatsoever if there is something called ‘I.’ If your position is that there is no ‘I,’ who can be afraid?” (IX.52-56)

So there is no reason to fear emptiness, because it is emptiness that frees those who contemplate it from fear and its contemplation is necessary to follow the way of the bodhisattva. Even hīnayānists have no good reason to fear emptiness because they agree that there is no self that can be harmed by it.