Section 1: Pranadhikaranam: Topic 9 (Sutra 23)
The word 'Prana' must be understood as Brahman.
Ata eva Pranah I.1.23 (23)
For the same reason the breath also refers to Brahman.
Ata eva: for the same reason; Pranah: the breath (also refers to Brahman).
As Prana is described as the cause of the world, such a description can apply to Brahman alone.
"Which then is that deity?" 'Prana' he said. Regarding the Udgitha it is said (Chh. Up. I-10-9), 'Prastotri' that deity which belongs to the Prastava etc.
"For all the beings merge in Prana alone and from Prana they arise. This is the deity belonging to the Prastava" Chh. Up. I-11-4. Now the doubt arises whether Prana is vital force or Brahman. The Purvapakshin or opponent says that the word Prana denotes the fivefold breath. The Siddhantin says: No. Just as in the case of the preceding Sutra, so here also Brahman is meant on account of characteristic marks being mentioned; for here also a complementary passage makes us to understand that all beings spring from and merge into Prana. This can occur only in connection with the Supreme Lord.
The opponent says "The scripture makes the following statement: when man sleeps, then into breath indeed speech merges, into breath the eye, into breath the ear, into breath the mind; when he wakes up then they spring again from breath alone." What the Veda here states is a matter of daily observation, because during sleep when the breathing goes on uninterruptedly the functioning of the sense organs ceases and again becomes manifest when the man wakes up only. Hence the sense organs are the essence of all beings. The complementary passage which speaks of the merging and emerging of the beings can be reconciled with the chief vital air also.
This cannot be. Prana is used in the sense of Brahman in passages like 'the Prana of Prana' (Bri. Up. IV-4-18) and 'Prana indeed is Brahman' Kau. Up. III-3. The Sruti declares "All these beings merge in Prana and from Prana they arise" Chh. Up. I-11-5. This is possible only if Prana is Brahman and not the vital force in which the senses only get merged in deep sleep.