It is called: rājavidyārājaguhya–yoga: rājavidyā is the king–knowledge; rājaguhya is the secret of secrets.
You might therefore say that this chapter takes you to the very bottom of the essence of the whole teaching of the Gita. The teaching of the Gita is fundamentally an answer to the questions of Arjuna and in his formulation of the question there was one very important missing point: it was the most capital missing point. In his formulation of the question, he had insisted upon himself, his relatives, his sense of right, his sense of wrong, the consciousness of Dharma which arises out of the considerations of the society, kula, and the conflict between one set of right against another set of right. To fight for justice was right; to prevent the slaughter of people which will ultimately lead, according to him, to the destruction of the Dharma of the whole clan, to prevent this kind of a slaughter is also right. Now, both rights, if there was one against the other, there was some difference in the scale, one better than the other, one wrong against one right, it was easy to decide. But when the two things are right, then he could not decide what is to be done, and yet he decided that he will not fight: even undecided, he decided he will not fight. This was the condition of Arjuna’s question when he says: ‘Now tell me decisively what I should be doing’.
And we had pointed out that the very first starting point of Sri Krishna’s answer which begins in chapter n°2 is to point out to Arjuna that there is a difference between the Mutable and the Immutable; that which is Perishable and that which is Imperishable and He said that ‘while you seem to be speaking the language of the wise, you are missing out one thing which always the wise think of, and that is to think of the Imperishable’. That is the starting point. In other words the one thing which was missing in the premises of Arjuna was the consideration of the Imperishable, the omission to bring into the picture that there is a Reality which is immortal, Reality which is immutable, Reality which is imperishable. And the entire Gita is nothing but to bring this premise in the centre of the whole teaching, the whole answer. Sri Krishna says that ‘unless you bring that premise into the argument in fullness, you will not be able to resolve the problem that you are facing’.
Little by little this is being expounded: what is the nature of the Imperishable. In the 3rd & the 4th chapters a hint is given that that Imperishable is Himself: mām, mayi, ahaṁ, these are the different words that Sri Krishna uses to describe that Imperishable: ‘It is Me, it is I, it is…’, and then ‘It is the Lord’: it starts with the statement of the Imperishable, then gradually, it enters into a language in which the Imperishable is described as the Lord. Then He also said that that Lord is capable of descending on this earth and the entire idea of the Avatar is described. That is the supreme revelation in chapter n°4, where Sri Krishna declares Himself to be the Avatar. In chapter n°5 & 6 a kind of synthetic proposition is made to describe how the Imperishable and the Lord it is the same Reality, and the synthesis of the Imperishable and the Lord, the synthesis of the Impersonal and the Personal is indicated; but it is still very slight.
When you come to the 7th chapter, then you have a much more explicit statement of what is this Imperishable which is the Lord, and Sri Krishna explains that this is the Lord who has got two natures. A very striking statement is made and He says: ‘I have got a lower nature and I have a higher nature’, and this is what you have dealt with at length. And in this exposition, Sri Krishna explains what is the origin of the ‘Jiva’, a knowledge which is so important for each one of us because each one of us is a Jiva. Therefore as far as we are concerned for us to know the origin of us, that our own ‘self’ what we call ‘me’ is nothing but a partial manifestation of the Supreme Himself, of that Lord Himself. Therefore to know that our own being is rooted in the supreme Lord and that supreme Lord is manifesting through His own power, which is in itself originally divine, which somehow becomes un–divine; but the origin of the Jiva is in the ‘divine nature’, not in the un–divine nature. So, our own position in the whole world is basically rooted in the supreme Lord who manifests Himself in divine nature as a result of which, we as an individual, each one of us as an individual partakes of the nature of the supreme Lord and the supreme divine Mother: mamaivāṁśaḥ, the individual is my own portion, and parā prakṛtir jīvabhūtā, the Para Prakriti is of the nature of the Jiva, these complex sentences praise about the individual gives us the fundamental self–knowledge. It is always said: ‘know thyself’; ask your question: Who am I? What am I? And this question is particularly answered in chapter n°7 and you are told that basically you are not what you think to be: you think to be ‘ego’, as little ahaṁbhāva, which is connected with manas and buddhi, but all the three manas, buddhi and ahaṁkāra, they belong to the Apara Prakriti, whereas ‘you’, you belong to Para Prakriti, you belong to the higher nature. Having belonged to the higher nature you know how to relate yourself with the divine nature and with the supreme Lord, the secret of this relationship is yet not fully manifested in chapter n°7.