The Iyengar community traces its philosophical origins to Nathamuni, the first Sri Vaishnava acharya, who lived around 900 CE. He is traditionally believed to have collected the 4,000 works of Nammalvar and other alvars, the poet-saints of southern India who were intensely devoted to Vishnu on both an emotional and intellectual plane. The belief is that he set this collection - commonly called the Tamil Prabhandams - to music, and he introduced the devotional hymns of the alvars into worship, thus mixing their Tamil Veda with the traditional Vedas written in Sanskrit. A scriptural equivalence was accepted by the community that formed in acceptance of his works, with the Sanskrit texts considered to be metaphysical truth and the Tamil oral variants to be based on human experience of the same. This community became immersed in the dual-language worship in temples where issues of caste were of no concern.