This shloka completes the definition of Puruṣottama.

In 15.16, two puruṣas were introduced: kṣara-puruṣaḥ and akṣara-puruṣaḥ. Kṣara is the entire manifest material universe — all visible bodies, objects, worlds, and changing experiences. Akṣara, in this specific context, is not Brahman. It is unmanifest matter, māyā, the causal condition from which the manifest universe arises. In 15.17, Bhagavān introduced the third principle, uttama-puruṣaḥ, the consciousness principle that is different from both kṣara and akṣara. Now 15.18 says why that consciousness is called Puruṣottama. The PDF’s explanation is very clear that Puruṣottama here means nirguṇa caitanyam, not merely a particular saguṇa form.

The verse begins: yasmāt kṣaram atītaḥ aham — because I am beyond kṣara. Here “I” means Bhagavān’s real nature as consciousness. Atītaḥ means gone beyond, transcending, not limited by. The consciousness principle is beyond kṣara because it is not part of the changing manifest universe. The body changes, the mind changes, objects change, worlds change, and experiences change. Consciousness is the awareness because of which all these changes are known, but it is not itself one of the changing things.

Then Bhagavān says: akṣarāt api ca uttamaḥ — and I am superior even to akṣara. This is very important. A seeker may understand that the visible body and world are changing, but may still mistake the subtle causal condition, māyā, or deep causal stillness for the final truth. Bhagavān prevents that error. Even the unmanifest causal matter is not the final Self. Puruṣottama is superior to akṣara also, because akṣara here is still matter. It is subtler than visible matter, but it is not consciousness.

Therefore the verse says: ataḥ asmi loke vede ca prathitaḥ puruṣottamaḥ — therefore, in the world and in the Vedas, I am well known as Puruṣottama. The name is not accidental. Uttama-puruṣaḥ means the highest Puruṣa. When the words are reversed, it becomes Puruṣottamaḥ — the Puruṣa who is highest because He is beyond kṣara and superior to akṣara. This is the essence of the chapter’s title, Puruṣottama-yoga.

“Known in the world” means that in the religious and devotional world, Bhagavān is praised as Puruṣottama. “Known in the Veda” means that the śāstra reveals this same reality as the highest truth. But the seeker must understand the word deeply. Puruṣottama is not merely a form located in one place. Forms such as Kṛṣṇa, Viṣṇu, Śiva, Rāma, Devī, and others are sacred supports for worship and meditation. But the final meaning of Puruṣottama in this chapter is formless consciousness. Formless Viṣṇu, formless Śiva, formless Kṛṣṇa, and formless Rāma are not different. The destination is nirguṇa caitanyam.

So this shloka protects us from two mistakes.

The first mistake is identifying with kṣara: “I am the body, mind, role, personality, experience, or world.” All these are changing.

The second mistake is stopping at akṣara: “I am the causal blankness, unmanifest state, or māyā.” Even that is not the final truth.

Bhagavān says: I am beyond kṣara and superior to akṣara. Therefore I am Puruṣottama. The real nature of Bhagavān, and the real nature of the Self, is the consciousness that is independent, changeless, and not objectifiable. This is why the chapter is named Puruṣottama-yoga.