Knowledge of the Three Truths
Tattva-jñāna is knowledge of the three tattvas (ontological realities) of Vishishtadvaita: (1) chit — the realm of conscious beings (jīvas/ātmans), which are eternal, spiritual, and dependent on Brahman; (2) achit — the realm of insentient matter (Prakṛti/pradhāna), which is the material cause of the physical universe; and (3) Īśvara — Brahman/Paramātman/Śrīman Nārāyaṇa, the Lord who is the inner self and controller of both chit and achit.
Piḷḷai Lokācārya's Tattva Trayam
Piḷḷai Lokācārya's work Tattva Trayam (also known as the Three Truths) provides a systematic treatment of these three realities in accessible Maṇipravāḷam. Each tattva is defined by its essential nature (svarūpa), its essential qualities (svabhāva), and its essential activities (svabhāva-kārya). Understanding all three correctly is the prerequisite for meaningful pursuit of liberation.
Why All Three Matter
Knowing only Brahman (without knowing the jīva's real nature) leads to Advaita's error of identity. Knowing only the jīva (without understanding Brahman) leads to individualism and atheism. Knowing only the relationship (without both terms) is empty. Tattva-jñāna requires all three simultaneously — and their specific relationship (Brahman as the inner self of both chit and achit) is the distinctive contribution of Vishishtadvaita.
Prerequisite for Prapatti
Sri Vaishnava ācāryas teach that meaningful prapatti requires some degree of tattva-jñāna — not scholarly mastery, but genuine understanding of what one is surrendering (the jīva), to whom one is surrendering (the Lord), and why (the jīva's essential dependence). This understanding makes prapatti a meaningful and complete act rather than a mechanical gesture.