स य एषोऽह्र्दय आकाशः। तस्मिन्नयं पुरुषौ मनोमयः। अमृतो हिरण्मयः॥

sa ya eṣo'hrdaya ākāśaḥ | tasminnayaṁ puruṣau manomayaḥ | amṛto hiraṇmayaḥ||

(Taittirīya Upaniṣad I.6.1)

Meaning: Inside the heart, there is an empty space (ākāśa – ether, atmosphere, supposed to fill and pervade the universe and to be the peculiar vehicle of life and of sound). In this space resides Puruṣa (individual soul or jīvātman). In fact, there is no difference between Paramātman and jīvātman. Only for the sake of convenience we use Paramātman (Cosmic Self) and jīvātman (individual self).  Puruṣa is in the form of a mental sheath or cosmic mind (manomaya - consisting of spirit; this is not mamayakośa, the mental sheath in the subtle body covering the soul). This is eternal and radiating like gold (hiraṇmaya; Śrī Sūktam says hiraṇmayīṁ).

The heart that is referred here is not the biological heart. This is heart chakra and its exact location is explained in Mahānārāyaṇa Upaniṣad (Nārāyaṇa Sūktam). “This heart is located one palm length down from Adam’s apple and one palm length above the navel. This is the Abode of the universe. It suspends like an inverted lotus. It is surrounded by nerves and blood vessels and there is small space and in this space resides un-decaying, all knowing (omniscient), Fire that radiates on all directions.  

Chāndogya Upaniṣad (VIII.1) establishes that what is within is also outside of our body. In other words, it says that both macrocosm and microcosm are the same. “Our body is the dwelling house of Brahman. Within that abode, there is a lotus (referring to heart chakra) and within that lotus, there is a space. This space in the heart is as big as space outside. Both heaven (higher cosmic plane) and earth (lower cosmic plane) are within It. Everything exists in this space. All our desires are in condensed form here, but It is free from all afflictions.” This goes to prove that Brahman is not only the cause, but also the effect.

Kaṭha Upaniṣad (II.ii) says, “Cosmic Self is one (single or numeric 1) and controls everything. It is also the innermost Self of all the beings.” It manifests as many through Its own power called Māyā, which plays dual role. Everything originates from It and dissolves into It. We have often heard about this verse and this explains this reality beautifully.

आकाशात् पतितम् तोयम् यथा गच्छति सागरम्।

सर्व देव नमस्कारः केशवं प्रतिगच्छति॥

ākāśāt patitam toyam yathā gacchati sāgaram |

sarva deva namaskāraḥ keśavaṁ pratigacchati ||

This verse says that rains drops fall from sky, only to go to ocean. Rain falls on the ground and excess water go to the rivers and ultimately rivers merge into ocean and the waters of ocean evaporates and goes back to ākāśa. Sky is always eternal. The rain drops are individual souls. Rain falls on different places, both good and bad. But ultimately the water only reach the ocean. From the ocean they reach ākāśa. This is just an example. The cause is the same and the destination is also the same. But the path is different. Some drops fall on mountains and rivers and oceans. Other rain drops fall on garbage and sewage. But water ultimately reach the ocean only. Keśava here means Brahman. To which ever gods we worship, ultimately the effect of worship goes only to Brahman. Kṛṣṇa says in Bhagavad Gītā (IX.23, 25), “Even those devotees endowed with faith worship other gods (anyadevatāḥ), worship me only, but with a mistaken identity. They reach only those gods. But those who worship me, come to me and they are freed from transmigration.”

Now the question is how to realize that Brahman within and outside is the same. This realization can happen only through working on breath and mind. Only here, starts real Self-inquiry “Whom am I”. The disciple asks his teacher this question. His teacher replies “You are Brahman”. Now the student begins to make inquiries on the Self within.