Then Gārgya Sauryāyaṇi asked him: Lord, which (faculties) sleep in this human being? Which remain awake? Which is the deva that sees dreams? Whose is that happiness? In what are all established?

This verse presents the fourth question of the Praśna Upaniṣad, focused on states of consciousness and the nature of the dreamer.

The student Gārgya formulates five profound sub-questions:

Kāni svapanti — which ones sleep? In sleep, the external senses withdraw: the eye does not see external objects, the ear does not hear. What happens to these faculties?

Kāni jāgrati — which remain awake? Something continues functioning in sleep: we breathe, the heart beats, the mind produces dreams. Which faculties remain active?

Katara eṣa devaḥ svapnān paśyati — which deva sees dreams? Dreams are experiences: there is a seer and objects seen. Who is that observer? Deva here means the luminous faculty, that which illuminates experience.

Kasya etat sukham — whose is that happiness? In deep dreamless sleep (suṣupti) there is deep peace. Upon waking we say “I slept well, I know nothing.” Who experienced that happiness? How can we remember it if we were unconscious?

Kasmin sarve sampratiṣṭhitāḥ — in what are all established? What is the common foundation of waking, dreaming and deep sleep? What remains constant through the three states?

These questions anticipate the teaching of the Māṇḍūkya Upaniṣad on the four states of consciousness (avasthā). They are the fundamental questions of yogic inquiry: who am I through all experiences?