Yāmuna (967–1038 according to Mesquita 1973) is one of the chief figures of the philosophy later known as Viśiṣṭādvaita Vedānta. In fact, to me one of the most intriguing questions regards his role in the formation of this school. It is only with Rāmānuja (who lived two generations after Yāmuna) that the school becomes clearly Vedāntic and it is not by chance that it is only Rāmānuja who decided to write a commentary on the Brahmasūtra. Moreover, not all of Yāmuna’s works are completely preserved (and their loss is not at all recent: as proved by Roque Mesquita (1973, 189–190) they were unaccessible already by the time of Veṅkaṭanātha, 1269–1370). Nonetheless, Yāmuna was a gifted philosopher and whenever one digs in his works looking for the background of one or the other tenet of Rāmānuja or Veṅkaṭanātha, one usually succesfully identifies a passage in Yāmuna which inspired Rāmānuja and Veṅkaṭanātha.
Still, Yāmuna, especially in his juvenile works, is still under the influence of a non-Vedāntic (and perhaps Naiyāyika) approach to Pāñcarātra (which might be due to the influence of his granfdather Nāthamuni, who wrote a lost Nyāya work). For instance, as convinvingly explained in Mesquita 1971, Yāmuna starts with the idea that God’s existence can be proven through inference (as with the Naiyāyikas) and only later moves on to the thesis that it can be proven only through the Sacred Texts (as with Mīmāṃsakas and Vedāntins). Thus, it seems that at least in part the history of Viśiṣṭādvaita Vedānta has been conditioned by a choice occurring during Yāmuna’s lifespan.
Mesquita’s analysis presupposes his accurate reconstruction of the internal sequence of Yāmuna’s works, mainly based on internal references:
The three siddhis are incomplete, whereas the Puruṣanirṇaya is lost. What could it have contained, given that there was already a text bearing almost the same title (puruṣa-nirṇaya seems a synonym of īśvara-siddhi)? Mesquita reconstructs part of its contents through quotations and references to it in Rāmānuja and especially Veṅkaṭanātha. It appears that the Puruṣanirṇaya might be the result of Yāmuna’s dynamic re-shaping of his initial project when he started his Ātmasiddhi. In fact, in the opening of the latter, he said he would have dealt also with God’s existence, a subject which must have been —within the Ātmasiddhi— abandoned, given that he then wrote a further work on this topic, the Īśvarasiddhi. The Puruṣanirṇaya might have, similarly, dealt with topics announced in the Ātmasiddhi. More interestingly, it might have contained the shift from the inference to God’s existence to the evidence out of the Sacred Texts alone (Mesquita 1973, p. 192). On top of that, it might have contained the argument about the identification of the Sacred Texts’ “God” with Viṣṇu.
Was Yāmuna for Rāmānuja like Utpaladeva for Abhinavagupta? And who is before your favourite Indian philosopher?
On Yāmuna’s, Rāmānuja’s and Veṅkaṭanātha’s distinct contribution to “Viśiṣṭādvaita Vedānta” see this post.