Members of the Sri Vaishnava sect of Hinduism, especially the Iyengars (Sri Vaishnavas who are Brahmanas), are divided into two sub-sects, Thenkalais and Vadakalais. These two sub-sects both agree on the Visishtadvaita philosophy of Ramanujacharya that characterizes the Sri Vaishnava belief system, but they have several fine-grained but important doctrinal differences; my answer here lays out the main points of dispute. In this question, I asked about one such difference. Now I'd like to ask about another difference, described in this webpage:
(i) Kaivalya is inferior to Paramapada
(ii) Kaivalya is not eternal
(iii) Kaivalya is situated Outside Paramapada
(ii) Kaivalya is eternal
(iii) Kaivalya is within Paramapada but in its outermost parts.
This is also mentioned in this webpage quoting from a journal paper:
Kaivalya (Isolation)-Moksa (or Soul-sight or Soul actualization; or the State of Atomic-aloofness).
[Vadakalais] say that this state is temporary.
[Thenkalais] say it is perennial. The soul wished for it, strove for it, and got it. What it got is eternal, by its own making. Where, then, is extrication from this state? Being a spiritual state, return to material planes is cut off. Being a soul-state, rising to Divine-planes or God-state is shut off.
For those who don't know, Kaivalya, AKA Ekatva, is a conception of Moksha where an individual completely realizes the nature of his Atma and achieves a state of abstract and impersonal self-actualization. It is the highest goal for followers of Adi Shankaracharya's Advaita Vedanta. Vaishnavas, in contrast, think that even higher than Kaivalya is the attainment of Vishnu in his abode of Paramapada. (According to Advaita, the individual's Atma is the same as Paramatma, but in Visistadvaita they're not the same, which means that an individual who tried to realize his Atma would fall short of attaining Vishnu.)
So the issue under consideration is, do souls who follow Advaita and attain Kaivalya ultimately return to the cycle of birth and death, or do they remain in Kaivalya eternally? Vadakalais say that Kaivalya is temporary and that souls ultimately return to Samsara where they'll have further opportunity to attain Paramapada. Thenkalais, on the other hand, say that souls who attain Kaivalya never leave it, and are thus unable to progress to the inner parts of Paramapada where Vishnu is.
So my questions are,
- Why do Vadakalai Sri Vaishnavas believe that Kaivalya liberation is not eternal?
- What arguments have Vadakalai Acharyas like Vedanta Desikan made on this subject?
- Are there any scriptures that Vadakalais believe demonstrate the temporary nature of Kaivalya?