adhva diverges from this radically by insisting it is not knowledge, but bhakti to God(as Lord Vishnu, not just any God, only Vishnu is God in his theology) whereby you win his grace. However, there are terms and conditions, each soul has intrinsic amount of ability to do bhakti and win his grace. There is one class that can do enough bhakti to win his grace; another class that can never do enough to win his grace so they keep circling about in samsara, and there is another that are eternally condemned to hell.
This is also a misunderstanding.
What madhavacharya is talking about, when he talks these classes, is that he is talking about three categories. This categories themselves are not fixed or eternal, but rather a Jiva can move through them, as they again Jnana. For example, there is a class of jivas who are eternally present in Vaikuntha with Narayana (they are called Siddhas and they will, in their current state exist eternally with Narayana). There is another class of jivas who are in eternal rebirth (which means that if left in their state, they will continue to undergo the cycle of birth and rebirth). and there is another class in tamo guna who are in hell (eternally if left in that stage). However a Jiva can elevate themselves up into the position of Siddha through Sadhana (assuming one has human birth). Otherwise, it would be impossible for us (in this world who are in rebirth) to attain Moksha and therefore Madhavacharya would have no need to put forth any philosophy regarding this.
I shall present proof, from the commentary of Madhavacharya himself (on Gita 8.16)
"Starting with Brahma the designer and architect of creation who resides on the crest of Mt. Meru in Brahmaloka which is the highest material planet
all living entities are subjected to samsara or the perpetual cycle of birth and death. Therefore it is stated in the Narayana Kalpa that: In all cases concerning the material worlds from the highest Brahmaloka down through the heavenly planets to the worlds of humans there is no possibility of attaining the Supreme Lord without
moksa or liberation.
Now begins the summation.
Liberation from samsara and attaining the Supreme Lord Krishna is only possible through bhakti or exclusive loving devotion to Him exclusively. Those whose goal is to enjoy in the heavenly planets which is free from disease, decrepitude and old age will reach those worlds and enjoy; but they will take birth in a womb again for attainment of the Supreme Lord was not their goal; but the devotees of Lord Krishna whose only goal is Him attain moksa."
The purport here is simple, all living entities in this world are in the cycle of Samsara. However by the process of Moksha, these entities can be liberated. There is nothing in Dvaita about intrinsic amount of Bhakti, because all living entities in this world a
jiva tattva and therefore equal.
Anyway, to me this debate seems pointless, unless we can define some characteristics of Classical Hinduism that we can use to apply to each of the schools. As for the validity of Dvaita, I am pretty sure I could present a scriptural defense of it.
Mind you my school believes that the atma and Brahman are both one and also different, like a drop from the ocean. The jivatmas is only a partial manifestation of Brahman. Prabhupada called it part and parcel of God. I can defend this surely. For example this verse in Mundaka Upanishad very clear shows the distinction between Jivaatma and Ishwara:
dvā suparṇā sayujā sakhāyā samānaṃ vṛkṣaṃ pariṣasvajāte /
tayor anyaḥ pippalaṃ svādv atty anaśnann anyo abhicākaśīti // 4.6 //
Like two birds of golden plumage, inseparable companions, are perched on a branch of the same tree. One of them tastes the sweet and bitter fruits of the tree; the other, tasting neither, calmly looks on.
[this verse shows that in the tree of the body there are two different and distinct birds. One is the jivatma who is eating the fruits of the tree, i.e enjoying his karma, and the other is Ishwara, of Paramatama, who is watching]
samāne vṛkṣe puruṣo nimagno anīśayā śocati muhyamānaḥ /
juṣṭaṃ yadā paśyaty anyam īśaṃ asya mahimānam iti vītaśokaḥ // 4.7 //
On the same tree, the individual self (jiva), deluded by forgetfulness of his identity with the divine Self, bewildered by his ego, grieves and is sad. But when he recognizes the other as the Lord worshipped by all and His glory, he becomes free from grief.
[The jiva suffers because of ignorance of the Paramatma, the sumpreme Lord, but when she recognizes Him, she becomes free from grief]
These two verses from the Upanishads prove the different between the jivaatma (us) and Ishwara. They both reside in the body but they are not the same. There are various other verses in Upanishads that support this.
It is true, that Brahman and Atman are one in one sense but there is also some difference between them. When the Upanishads talks about Atma, they are can refer to two different objects. The first Atma is the Paramatma (or Ishwara, the Sumpreme Soul, who is all pervasive, all knowing, the object of sacrifices etc).. The second Atma is jivaatma or us the souls, who are parts and parcels of Brahman, like a drop of an ocean. The jivatma and the paramatma are not identical.
The argument for this is that sruti describes Atman to be all pervasive and all knowing, but it is evident that we are not all pervasive (because if we were, then it would be impossible for the soul to move, but the soul does move as it transmigrates through various bodies). Therefore we cannot be the
all pervasive Atman that is described in Sruti. In a similiar way, Atman is all knowing, but we cannot know anything that is outside out scope of experience (I cannot know your thoughts, nor can you know mine). Therefore we cannot be the all knowing Atman that is described in Sruti.