We have explained in our introduction that all the commentaries in the market, they are simply presentation of the particular commentator's personal view. That is not Bhagavad-gītā. If you want to understand Bhagavad-gītā, then you should understand as they are said. You don't interpret in your own way.
Now, because there should be some doubt of the ordinary man, that "How Kṛṣṇa could say to the sun-god?" that is explained in the next verse. Because Arjuna was taking instruction from Kṛṣṇa, he knew Kṛṣṇa, what He is. Otherwise he would not have accepted him as a spiritual master. But because others would doubt, "This is fictitious that Kṛṣṇa said to the sun-god. How it is possible?" so you will find Arjuna said, "The sun-god Vivasvān is senior by birth to You. How am I to understand that in the beginning You instructed this science to him?" Kṛṣṇa is taking our position, er, Arjuna. Persons who are thinking of Kṛṣṇa as ordinary person, so Arjuna is trying to clear that point, that Kṛṣṇa is not ordinary person. He is the Supreme Personality of Godhead. Therefore he has put this question, that "The sun-god Vivasvān is senior by birth to you."
Sun-god, Vivasvān, the sun planet, father of Manu... Manu's age we cannot calculate. About forty millions of years ago Manu was born, and his father, we do not know what is his age. So how it is possible, if Kṛṣṇa is ordinary man, He spoke to him? That is being cleared. So what He answered? "The Blessed Lord said, 'Many, many births both you and I have passed. I can remember all of them, but you cannot." That is the difference between God and man. That is the difference between God and man. We cannot remember. Even we cannot remember what I did at this time yesterday. That is our forgetfulness, is our nature.
To commit mistake, to forget, to be illusioned, to be cheated, imperfection of the senses—these are our qualifications. Every one of us, anyone who is in this material world, they are subjected to these defects: he is sure to commit mistake—"To err is human"—he is subjected to be illusioned, and he has a cheating propensity. Just like a mundane scholar. I do not wish to name. A mundane scholar, he admits, his introduction, that it is very difficult to interpret Bhagavad-gītā in one's own way. It is so tightly fitted. Actually it is so. Unless you contradict yourself, you cannot interpret Bhagavad-gītā according to your own way.