Anukritestasya cha I.3.22 (85)

On account of the acting after (i.e. the shining after) (that after which sun, moon, etc. are said to shine is the Supreme Self) and (because by the light) of Him (everything else is lighted).

We read in Mundaka Upanishad II-2-10 and Kathopanisad II-ii-15 "The Sun does not shine there nor the moon and the stars, nor these lightnings, much less the fire. After him when he shines everything shines; by the light of him all this is lighted."

Now a doubt arises whether "he after whom when he shines everything shines, and by whose light all this is lighted" is some effulgent substance, or the Supreme Self.

The 'shining after' mentioned in the text "After him when he shines everything shines" is possible only if the Supreme Self or Brahman is understood. Another Sruti declares of that Supreme Self, "His form is light, his thoughts are true" Chh. Up. III-14-2. "Him the gods worship as the light of lights, as immortal time" Bri. Up. IV-4-16.

The clause "On account of the acting after" points to the 'shining after' mentioned in the text under discussion.

That the light of the Sun etc., should shine by some other material light is not known. It is absurd to say that one light is lighted by another. We do not know of any physical light, except the sun, that can light Brahman.

The manifestation of this whole universe has for its cause the existence of the light of Brahman, just as the existence of the light of the sun is the cause of the manifestation of all form and colours. Brahman is self-luminous. It remains in Its own glory. It illumines the sun, the moon, the stars, the lightning, the fire, the senses, the mind and the intellect and all objects. It does not need any other light to illumine it. Sruti texts like "Brahman is the light of lights (Jyotisham Jyotih)" clearly intimate that Brahman is Self-effulgent. It is quite possible to deny the shining of sun, moon etc., with reference to Brahman, because whatever is seen is seen by the light of Brahman only. As Brahman is Self-effulgent, it is not seen by means of any other light.

Brahman manifests everything else but is not manifested by anything else. We read in Bri. Up. "By the Self alone as his light man sits" IV-3-6. The word 'Sarvam' denotes that the entire world of names and forms is dependent on the glory of Brahman. The word 'anu' intimates that the reference is to Brahman because it is from Him that all effulgence is derived.

Api cha smaryate I.3.23 (86)

Moreover the Smriti also speaks of him i.e. Brahman to be the universal light.

An argument insupport of Sutra 22 is given.

The Smriti or Gita also says so. In Gita, Chapter XV-6 we read "Neither the sun, nor the moon, nor the fire illumines that, having gone into which men do not return, that is my highest seat." And "The light which abiding in the sun illumines the whole world and that which is in the moon and that which is in the fire, all that light know to be mine" XV-12.