The term nāstika (from Sanskrit 'na asti' — 'it is not' or 'does not exist') refers classically to those who deny the authority of the Vedas (Śruti) as the primary source of knowledge about transcendent reality. In the broader Hindu philosophical tradition, nāstika-mata (nāstika doctrine) encompasses schools such as the Chārvāka (strict materialism), early Buddhism, and Jainism, all of which — however different from each other — do not accept the Vedas as the eternal and authoritative revelation.
In the Viśiṣṭādvaita tradition of Rāmānujāchārya, the contrast between āstika and nāstika is fundamental. The āstika accepts three sources of valid knowledge (pramāṇas): pratyakṣa (direct perception), anumāna (inference), and śabda (verbal testimony, specifically the Vedic revelation). The nāstika, in Mīmāṃsaka and Vedāntic usage, is one who reduces valid knowledge to only perception and inference, denying that Vedic testimony has a special epistemic status.
The Śrī Vaiṣṇava tradition goes further and identifies a hierarchy of nāstika-error: those who deny scriptural authority entirely; those who accept scripture but misinterpret it to deny the personal nature of Bhagavān (as the Advaita school is sometimes argued to do in Śrī Vaiṣṇava polemic); and those who accept a God but deny that He has a specific form, a divine abode, and a relationship with individual souls (jīvas). The tradition's goal is to defend the full richness of Viśiṣṭādvaita against each of these reductions.
In the daily life of the Śrī Vaiṣṇava, nāstika views are to be avoided not primarily as an intellectual matter but as a spiritual one. The ācāryas teach that association with those who actively argue against the reality of Bhagavān and the Vedic revelation corrupts one's śraddhā (faithful confidence) over time. The Srivachana Bhūṣaṇam and similar texts identify this association as among the obstacles (virodhi) to the spiritual path.
It is important to note that the tradition does not counsel contempt for nāstikas as persons. Rather, as with Abhāgavatas, the attitude recommended is compassion — the recognition that nāstika views represent a form of spiritual blindness, and that the appropriate response is patient teaching, prayer for their awakening, and maintaining one's own clarity of conviction without becoming entangled in fruitless debate. Rāmānuja himself engaged philosophically with nāstika arguments throughout his Śrī Bhāṣyam, demonstrating that the appropriate response to nāstika claims is reasoned refutation, not dismissal or hostility.