"I instructed this imperishable science of yoga to the sun-god, Vivasvan, and Vivasvan instructed it to Manu, the father of mankind and Manu in turn instructed it to Iksvaku."
When Arjuna heard Krishna explain this he appeared to become bewildered. He was thinking that Krishna is his friend and they were both born around the same time so how is it possible that Krishna spoke the Bhagavad-gita to the sun-god some millions of years ago? So Arjuna questioned Krishna: "The sun-god Vivasvan is senior by birth to You. How an I to understand that in the beginning You instructed this science to him?" (Bg. 4.4)
We may think that, "Arjuna is an accepted devotee of the Lord, so how could he not believe Krishna's words?" In reality Arjuna does accept Krishna's words and of course believes everything Krishna says without question, however this conversation of the Bhagavad Gita between Krishna and Arjuna was not only for the benefit of Arjuna. Arjuna is conscious of this so here he is not inquiring for himself. He is asking this question on behalf of the people who do not believe in the Supreme Personality of Godhead, the demons who do not like the idea that Krishna should be accepted as the Supreme Personality of Godhead. So it is only for the benefit of the demons that Arjuna inquires on this point, as if he himself was not aware of the Personality of Godhead, Krishna. We will see in the Tenth Chapter that Arjuna knows perfectly well that Krishna is the Supreme Personality of Godhead, the source of everything and supreme authority of transcendental knowledge.
It is confusing for the general population because Krishna appeared on this earth as the son of Devaki. So the ordinary people find it very difficult to understand how Krishna could remain the original, eternal Supreme Personality of Godhead and still appear as a baby in the arms of His mother. So it is only to clarify this point for the general public that Arjuna is appearing to be bewildered on this point and asking Krishna the question: "Krishna we were both born around the same time so how is is possible that You spoke the Bhagavad Gita to the sun-god millions of years ago?" Krishna is the supreme authority accepted by all, only the demons reject Him, so by asking this question Arjuna is giving Krishna the opportunity to speak authoritatively on this point and record the answer for everyone's benefit in the Bhagavad Gita.
Krishna answered Arjuna's question by saying: "Many, many births both you and I have passed. I can remember all of them, but you cannot." (Bg. 4.5) So this is a very important revelation by Krishna. Devotees
like Arjuna are constant companions of the Lord, and whenever the Lord incarnates, the associate devotees also incarnate in order to serve the Lord in different capacities. Arjuna is one of these devotees, and in this verse it is understood that some millions of years ago when Lord Krishna spoke the Bhagavad Gita to the sun-god Vivasvan, Arjuna, in a different capacity, was also present. But the difference between Krishna and Arjuna is that Krishna can remember speaking the Bhagavad Gita to the sun-god millions of years ago but Arjuna, although he was there with Krishna, can not remember anything about this incident or anything about any of his past births. This is one of the proofs that the living entities can never become equal to the Supreme Lord.
Anyone who is a constant companion of Krishna like Arjuna is certainly a liberated person but even a liberated person can not be equal to the Lord. That is the difference between the part-and-parcel living entity and the Supreme Lord. In the Brahma-samhita Krishna is described as infallible (acyuta) which means that He never forgets Himself even though He is in the material contact. Therefore the Lord and the living entity can never be equal in all respects, even if the living entity is as liberated as Arjuna.
We can note here that a living entity forgets everything due to his change of body, but Krishna remembers because He does not change His eternal body full of knowledge and ever-increasing bliss. For Krishna there is no distinction between His body and Himself. Everything related to Him is spiritual whereas the conditioned soul is different from his material body. But Krishna's body and His self are identical therefore His position is always different from the position of the ordinary living entity, even when Krishna descends to this material
So we can understand that Krishna and His pure devotees are eternally related and whenever Krishna appears in the material world His confidential devotees also appear in the same place so they can render service to Krishna and in this way the pastimes of Krishna become very much enriched. If Krishna was alone then what could we speak about Krishna--but Krishna is not alone, Krishna is always with His devotees
and the devotees are always with Krishna. The pastimes of Krishna in Vrindavan are very relishable because Krishna is there with all the residents of Vrindadvan and from this example we can see what spiritual life actually is.
Spiritual life is similar to material life. The only difference is that in spiritual life everyone is serving Krishna, in material life everyone is serving maya. So to transform our consciousness from material life to spiritual life simply requires transforming our consciousness from material consciousness to spiritual consciousness. And in this Kali-yuga the most powerful and the only practical way to do this is simply by chanting:
Hare Krishna Hare Krishna Krishna Krishna Hare Hare
Hare Rama Hare Rama Rama Rama Hare Hare