Heat and rain, death and the deathless: nothing stands apart from him.

Advaita Vedānta

The Advaita reading takes sat and asat as effect and cause while guarding carefully against two errors. The Lord is not the utterly unreal: in himself, and as both effect and cause, he is both the real and the unreal. The 'existent' (sat) is the effect, the thing connected with a cause; the 'non-existent' (asat) is the cause itself, of unmanifest name and form. Against the void-doctrine (that all is mere nothing), the point is pressed that if the Lord were utterly non-existent, the very idea of cause and effect would have no substrate to stand on. Yet there is also no absolute existence of the effect, since scripture says 'the modification is a beginning in speech only,' nor absolute non-existence of the cause, since scripture asks 'whence indeed.' On this basis the world is taken to be in truth unreal and the substrate alone real, and the address 'Arjuna' is read as a hint that the Lord, so understood, is ever free of all limiting adjuncts and ever pure. The fruit promised to those who worship by such knowledge is liberation, whether immediate or gradual.

Śaṅkarācārya · Śrī Ānandagiri · Dhanapati Sūri · Madhusūdana Sarasvatī

Viśiṣṭādvaita

This school reads sat and asat as the present versus the past-and-future, and is emphatic about how the identity is to be heard. The existent is what is now present; the non-existent is what is past and what is to come. Because every conscious and unconscious thing, in every state, is the Lord's body, he abides with that thing and that mode, and so it can be said, 'it is I myself.' One source warns the reader explicitly: 'I am sat and asat' must not be heard as 'I am being and non-being equally,' but as 'I am the supporter of both,' the inner ground without which neither the manifest being nor the unmanifest cause would stand. The whole world, abiding as divided names and forms, is the Lord's body; those who dwell on this with the knowledge of oneness and worship him are the great souls.

Rāmānujācārya · Vedānta Deśika

Dvaita

This school takes sat as the effect and asat as the cause on lexical grounds: because the effect is of manifest form it is called 'existent' by the wise, and because the cause is of unmanifest form it is named 'non-existent.' One source meets a sharp objection: since the non-existent cannot be controlled, saying 'I am being and non-being' would seem unfitting; the reply is that 'being' names the effect and 'non-being' the cause through the verbal root 'sad' meaning 'to go,' so both terms apply to controllable realities. Crucially, this school does not let the verse collapse the Lord into the world. It cites the Bharata that there is a world which is both non-existent and existent, and 'that which is beyond the existent and the non-existent.' The conclusion drawn is that Brahman is supreme, beyond the universe which is being and non-being.

Madhvācārya · Śrī Jayatīrtha

Śuddhādvaita

This school frames the verse within creation and the path of gradual liberation. Citing scripture that 'in the fifth oblation the waters come to be spoken of as purusha,' it reads 'I give heat' as showing the Lord to be both the doer of creation and the doorway to gradual release: through the sun's heat and rain, food is born, and so the Lord is the accomplisher of creation, this being cultivated for its use in sacrifice. One source reads the heating as done for the sake of the savouring of rasa, the rain itself being of rasa-form, drawn into the Lord and set within himself and then released again. Sat is the gross and visible, asat the subtle and unseen, and in the pure brahma-yajna even sat and asat, the very absence of worldly knowing-of-things, are the Lord, for all is Brahman, all is himself. The address 'Arjuna of pure form' is woven in to mark this purity of vision.

Vallabhācārya · Śrī Puruṣottama

Bhedabheda

This reading takes sat as the gross, the thing fit for ordinary dealings, and asat as the subtle, the unmanifest, not fit for ordinary dealings, concluding plainly that there is nothing whatever apart from the Lord. It then carries the thread into worship: those of right vision, free of desire, worship him as one, facing in all directions; others, also free of desire, worship him 'as distinct,' in many ways, apprehending him through each single form such as the rite. Both forms of knowledge-sacrifice are set over against the mere ritualists who are greedy for fruit, for whom the verse about the three-Veda knowers who pray for the way to heaven is then quoted.

Śrī Bhāskara

Bhakti

The devotional reading keeps the meaning close to the cosmic image and turns it toward wonder and worship. Sat is the gross and visible, asat the subtle and invisible, and all this is the Lord himself alone, so the seeker is told to reflect on this and worship him in the many ways. One source dwells at length on the pathos of not seeing him: the Lord glows as the sun and floods the world as Indra; fire consumes fuel which becomes fire, so both the killed and the killer are of his essence; whatever is mortal is his outward appearance and whatever is immortal is his very being. There is no nook anywhere in which he is not, yet creatures fail to see him, like waves saying there is no water, or one fallen into a well of nectar wishing to be pulled out, or a blind man stumbling on the wish-fulfilling stone and kicking it aside. From this the source draws a lesson: action done without this knowledge is no real action; even good actions become vain when not backed by insight.

Śrīdhara Svāmī · Sant Jñāneśvar

Modern

The modern voices differ mainly in how they fix the meaning of sat and asat. One insists, on Upanishadic grounds, that 'non-existence' never means nothingness: existence cannot come from nothing, so asat names the subtle, unmanifest cause (Mula-Prakriti), and for the Vedantin Brahman alone is truly sat because it is unchanging and ever-exists, while the manifested world is the unreal; for the worldly-minded, who perceive only gross forms, the manifest world is sat and both the unmanifest cause and Brahman are asat. This source also lays out the gross, subtle, and causal states of every object, illustrating with an orange's skin, pulp, and seed. Another takes the primary sense as 'imperishable' (sat) and 'perishable' (asat), noting that 'good' and 'bad' is a possible secondary sense, and observes that this pair, like 'death' and 'deathless,' echoes the Nasadiya hymn; the Gita, however, reverses the hymn's usage, applying sat to Para-brahman and asat to the visible world, while using the two together to include both the world and Brahman, and reads the whole passage as declaring the Lord's fatherly, motherly, friendly relationship to all beings. A third, a non-sectarian devotional voice, dwells on the sun's purifying work, drying up impurity and disease and the poison in herbs, drawing up water and returning it pure and sweet as rain to sustain all life, and concludes that since both the manifest and unmanifest are nothing but the Lord, the devotee is to see in every act and every thing only God.

Swami Sivananda · Lokmanya Tilak · Swami Ramsukhdas