Kāraṇatva — Bhagavān as the Cause of the Universe
Kāraṇatva designates Bhagavān's unique threefold causality in relation to the universe. In Indian philosophy, causation is analyzed into: upādāna-kāraṇa (material cause — what the effect is made of), nimitta-kāraṇa (efficient cause — the agent who acts), and sahakāri-kāraṇa (instrumental/cooperative cause — the tools and conditions). Viśiṣṭādvaita's bold claim is that Bhagavān alone is all three.
As upādāna-kāraṇa: The universe is made 'out of' Bhagavān — it is the transformation (pariṇāma) of Bhagavān's body (cit and achit in their subtle states). This is not pantheism because Bhagavān, as the soul of cit-achit, remains unchanged (nirvikāra) even as His body transforms. The Taittirīya Upaniṣad's 'sa brahma saṃskṛtya nirāsīt' ('From this, verily, all beings are born') is understood as Bhagavān's body (not His essential nature) becoming the universe.
As nimitta-kāraṇa: Bhagavān is the supreme agent who initiates, manages, and dissolves the universe (sṛṣṭi-sthiti-saṃhāra). This is His five-fold function (pañca-kṛtya) — creation, sustenance, dissolution, concealment, and grace. No secondary agent (Brahmā, Rudra) acts independently; they are all instruments through which Bhagavān's nimitta-kāraṇatva operates.
As sahakāri-kāraṇa: Bhagavān provides all the conditions and materials (time, the cosmic elements, the souls themselves) that enable the universe to manifest. He is 'the field and the knower of the field' simultaneously, enabling all cooperative causation.
This unified kāraṇatva is the philosophical basis for the Śrī Vaiṣṇava assertion that everything is Bhagavān's body — the universe did not emerge from something other than Brahman, nor did Brahman become unconsciously transformed into the universe. The world is real, Bhagavān is the cause, and the causal relationship does not diminish Bhagavān's absolute completeness (pūrṇatva).