The Two-Fold Scripture
Ubhaya Vedānta (Sanskrit: ubhaya = both + vedānta = end/culmination of the Vedas; 'both Vedāntas') is the foundational hermeneutical principle of the Śrī Vaiṣṇava tradition: both the Sanskrit Vedic corpus (Upaniṣads, Brahma Sūtras, Bhagavad Gītā, Purāṇas) and the Tamil Nālāyira Divya Prabandham are equally authoritative as śabda-pramāṇa (valid scriptural testimony).
Why This Is Revolutionary
In most Sanskrit Vedāntic traditions, Tamil vernacular texts are devotional but not formally equal to Sanskrit scripture. The Śrī Vaiṣṇava claim is stronger: Nāthamunigaḷ recognized the Divya Prabandham as Drāviḍa Veda (the Vedas in Tamil), and the tradition consistently treats pāsurams as having the same revelatory authority as Upaniṣadic mantras.
Rāmānuja's Practice
Rāmānuja exemplified ubhaya-vedānta in his works: the Śrī Bhāṣya interprets Brahma Sūtras through Sanskrit Vedic authority, while his Tamil liturgical tradition (at Śrī Raṅgam, introducing Divya Prabandham recitation in temple worship) treated the pāsurams as essential scripture. Vedānta Deśika's Tātparya-ratnāvalī further demonstrates the doctrinal alignment of the two Vedas.