Vedanta Sutra 4.4.3

AtmA prakaraNAt

3. The Atman is that "Highest Light";
because of the context. - 540.

COMMENTARY

That "Highest Light" mentioned in the Chandogya Upanishad is indeed the Atman (the Supreme Self), and not the Solar sphere, because the topic under discussion, where that passage occurs, refers to the Supreme. Though the word jyotiH is a common term, meaning both the sun and Brahman, yet this word here, on account of the topic under discussion, denotes the Supreme Self. As in the sentence "devo jAnati me manaH," the word deva is used in the sense of "You". The sentence means "you know my mind."

The word Atman, in this sUtra, refers to an All-pervading substance whose essential form is knowledge and bliss. The word Atman is derived from the root 'at' meaning "to go continuously, to obtain and to illumine." Thus Atman means that which illumines, secondly, that which is reached by the free souls, third, that which is all-pervading. So it applies both to the human soul as well as to the Supreme Lord. It has several meanings, like the word "Upanishad." And this entity Atman must be admitted to be a person. Because the descriptions of it, given in the passage under discussion is that of a person, it is called there "Uttama PuruSa", the Supreme. [See Chandogya Upanishad 8.12.3]

Therefore, the "Highest Light", which the freed soul attains to, is this Uttama Purusa, the Supreme Person, the Lord Hari: and is not the solar sphere.


References:

Chandogya Upanishad 8.12.3:

evam evaiSa samprasAdo'smAc charIrAt samutthAya paraM jyotir upasampadya svena rUpeNAbhiniSpadyate, sa uttamaH puruSaH, sa tatra paryeti, jakSat krIDan ramamANaH strIbhir vA yAnair vA jJAtibhir vA nopajanaM smarann idaM zarIram: sa yathA prayogya AcaraNe yuktaH, evam evAyam asmin zarIre prANo yuktaH

"He through whose grace this released soul, arising from his last body, and having approached the Highest Light, is restored to his own form is the Highest Person. The Mukta moves about there laughing, playing, and rejoicing, with women, carriages, with other Muktas of his own period or of the past Kalpas. (So great is his ecstasy) that he does not remember even the person standing near him, nor even his own body. And as a charioteer is appointed by his master to drive the carriage, just so is the Prana appointed to drive this chariot of the body."