Nārāyana - the Supreme Reality
The Supreme Reality or the Supreme Being is Nārāyana who is infinite in nature. He is omniscient, omnipotent, creator, preserver and destroyer of the world:
Nārāyana is the Supreme Soul and the only Lord of the universe. Nothing exists without Him. He is the cause as well as the effect of the creation.
Just as water, air, earth and sky are pervading the world, in the same way, Nārāyana is pervading the mind, intellect and vital breath (prāna) of things and beings. He is pure, attributeless and conscious self of the Universe. In Him, the world of creation exists and yet, He is beyond the world.
“The Highest Self (Nārāyana) is form-less, all-pervading, eternal, faultless, full of natural delight, composite of eternal knowledge (vijnāna), and without a body; but He is the creator, preserver and destroyer of the world; He heareth, standeth and goeth (walketh), taketh hold (of things), understandeth, and killeth (beings). But He doth not perform any work, being without any possessions, devoid of any movement, desire or attachment and activity. Having created the world, He resideth in it in a very detached manner.”
The Only Unchangeable Reality
Nārāyana has been described in a considerable number of verses as the only reality underlying various objects and beings of the world. He is immutable (avikāri), being above the influence of kāla (time) and māyā (illusion).
O Lord, You are the only unchangeable reality of this world; others are liable to change and decay. Being the primal cause (ādya kārana) of the creation You are above the changes caused by birth and death. O Nārāyana, You, being the Primal and Eternal Purusa, are free from any change and decay and, therefore, no limitation of any sort is applicable to You. Space, time and matter cannot measure or differentiate You. You are complete in Yourself.
Different Names of the Supreme Reality
Sankaradeva opines that there is one Supreme Reality - Parabrahma Nārāyana - and when this Supreme reality is viewed from different angles, it is referred to by different names like Brahman, Paramātmā and Bhagavat, eg. when the Supreme Reality is viewed as the creator or sustainer or destroyer of the world, it is then known as Isvara or Bhagavanta.
Brahman, Paramātmā and Bhagavat are the names of one Supreme Reality. The same reality is called by different names due to different characteristics, viewed from different angles of vision.
In his Nimi Nava Siddha Samvāda, a philosophical work based on the Book XI of the Bhāgavata, Sankaradeva has interpreted the above terms and has shown that those are but different names of the same Supreme Reality seen through different angles:
God as the director and controller of sense is known as the Paramātmā, and as the creator, preserver and destroyer of the world, He is Bhagavat. When God appears to Yogis in their meditation after the disappearance of ignorance, He is called Brahman. Brahman, Paramātmā and Bhagavat are the names of the One Reality. The same Reality is called by different names owing to different characteristics seen from different angles. (ekerese tinināma laksana bhedata).
[Sankaradeva, Nimi Nava Siddha Samvāda]