In Sanatana Dharma, the concept of the Supreme Personality of Godhead, also known as Bhagavan, represents the highest truth and the source of all that be. This concept is deeply rooted in our Vedic literatures. Sanatana means eternal. Dharma however does not refer to any sectarian belief systems like Hinduism, Islam, Christianity, Sikhism, etc. Dharma is the eternal function of the eternal living entities in relationship with the eternal Supreme Lord.
Dharma is different from the English word ‘Religion’. Religion is based on a person's faith, and therefore it can be changed. But Sanatana Dharma refers to that activity which can never be changed. To consider an example, liquidity can never be separated from water, nor can heat be separated from fire. Similarly, Sanatana Dharma can never be separated from a living entity.
All the great sages and Yogis are trying to realise this ultimate truth since time immemorial.
Brahmeti paramātmeti bhagavān iti śabdyate: “The Absolute Truth is called Brahman, Paramātmā and Bhagavān.” (SB 1.2.11)
So the absolute truth can be realised in these three aspects. However, the impersonalists can never go beyond the Brahman feature of the lord. Brahman is the impersonal bodily effulgence of the lord. As soon as we talk about sunshine, the presence of the Sun planet is automatically understood. Similarly, as soon as there is a concept of Brahmajyoti, there must be a source who is the provider of that effulgence. Paramatma is a higher stage of
realisation than the Brahman feature of the absolute truth. It is a partial representation of the Supreme Lord, who is present within the heart of every living entity as Kṣīrodakaśāyī Viṣṇu in his four handed form. The third and highest realisation of the absolute truth is the Bhagavan aspect of the supreme truth Krishna in his two-handed form, which is very pleasing to the devotees.
Bhagavan comes from two words, bhaga and van. Bhaga means opulence. Van means the one who is the possessor or the controller. So Bhagavan is the one who is the possessor and controller of all opulences, or riches of the three worlds and beyond. Bhagavan
ultimately means Lord Krishna, because he has been already accepted as the Supreme
Personality of Godhead in Srimad Bhagavatam. Kṛṣṇas tu bhagavān svayam (SB 1.3.28).
The Sanskrit word bhagavan is explained by the great authority Parasara Muni, the father of Vyasadeva. He explains that the one who simultaneously possesses six kinds of opulence in
full, namely:
1. All riches
2. All strength
3. All fame
4. All beauty
5. All knowledge
6. All renunciation
is called Bhagavan.
While Krishna was personally present on this planet, he displayed all these opulence at the same time in full. If we analyse carefully, it becomes evident that there is no second
competitor who can simultaneously exhibit all these six opulences in unlimited measure as Krishna did.
īśvaraḥ paramaḥ kṛṣṇaḥ
sac-cid-ānanda-vigrahaḥ
anādir ādir govindaḥ
sarva-kāraṇa-kāraṇam
(Śrī brahma-saṁhitā 5.1)
“Kṛṣṇa who is known as Govinda is the Supreme Godhead. He has an eternal blissful spiritual body. He is the origin of all. He has no other origin and He is the prime cause of all causes.”
Ishvar means controller. There are many controllers like Lord Siva, Lord Brahma, Indradev, Suryadev. But who is the Supreme Ishvar? He is Lord Krishna, as is evident by this verse. So he is īśvaraḥ paramaḥ.
ekale īśvara kṛṣṇa, āra saba bhṛtya
yāre yaiche nācāya, se taiche kare nṛtya
(CC Ādi 5.142)
“Lord Kṛṣṇa alone is the supreme controller, and all others are His servants. They dance as He makes them do so.”
In the Padma Purana, it is mentioned:
Aradhananam sarvesam visnor aradhanam param
“Of all types of worship, Visnu worship is supreme”
This statement is given by Lord Siva himself to Mother Parvati. This means that when one becomes a devotee of Lord Vishnu, or Lord Krishna, everyone is automatically served because he is the summum bonum of everything.
This statement can be found in Srimad Bhagavatam also as follows:
yathā hi skandha-śākhānāṁ
taror mūlāvasecanam
evam ārādhanaṁ viṣṇoḥ
sarveṣām ātmanaś ca hi
(SB 8.5.49)
“When one pours water on the root of a tree, the trunk and branches of the tree are
automatically pleased. Similarly, when one becomes a devotee of Lord Viṣṇu, everyone is served, for the Lord is the Supersoul of everyone.”
This can be understood because when we water the roots of the plant, all its branches and leaves are automatically served. We don't need to separately water the different elements of the tree. Another example is eating food. When the food reaches the stomach, the entire body is automatically nourished. But if we foolishly try to feed the fingers separately, then the result will not be very satisfactory.