So kāla's business is—kāla, time—to kill. So here also it is said, sa kālena iha, kālena mahatā. Mahatā is also kāraṇa, and kālena, by the influence of . . . that is now lost. Because it is a struggle. Our struggle for existence means we are trying to exist, but kāla is fighting to kill. That is going on. So kāla's business, time's business is to kill, but that system is now lost, is now killed by the influence of time. Sa kāleneha . . . yogo naṣṭaḥ parantapa.
Then, what is to be done? Sa eva ayaṁ mayā te adya yogaḥ proktaḥ purātanaḥ (BG 4.3). "So I have already begun to teach you about this Bhagavad-gītā. So it is not a new doctrine that I'm presenting before you." That, called . . . sa eva ayaṁ mayā te 'dya yogaḥ proktaḥ purātanaḥ. Purātanaḥ means the same old system, purātana. Purātana means purāṇa. Purāṇa means the old, historical events. Purāṇa. And this Mahābhārata, Mahābhārata is also . . . Mahābhārata, great history. And the Śrīmad-Bhāgavata is also called Mahā-Purāṇa, the great history of olden days.
So here also, the same word is used, that Kṛṣṇa says sa eva ayam: "This yoga system, the Bhagavad-gītā yoga system which I am now speaking to you, is very old. How old you can imagine, that I first spoke it to the sun-god." If you calculate only the age of Manu, it is about forty millions of years ago, to speak the minimum. So anyway, it is very, very old. Not that it is doctrine which is presented . . .
Just like in the modern educational system somebody is presenting some doctrine, and he's getting the title "Doctor," some new thesis. It is not like that. There is nothing to be researched. Eternal knowledge has nothing to be researched. There is no question of research. It is already established. Otherwise there is no meaning of eternal.
So this knowledge of Bhagavad-gītā is eternal. It is not a product of modern research or doctrine. Purātanaḥ sa eva. Sa evāyaṁ mayā te adya. Adya means "today." "Today I am speaking on the battlefield." Yogaḥ proktaḥ purātanaḥ.
"Why You are selecting me? Why You are selecting me and why this battlefield? You are speaking a philosophical doctrine and the science of God, and You are speaking to me. I am not a Vedāntist, I am not even a brahmin, I am not even sannyāsī. Ordinary gṛhastha. Of course, I have got the privilege that I am Your friend. So much so. Otherwise, yoga system is not to be spoken to me. Why You are speaking to me?" This may be questioned. Why specifically it was spoken to Arjuna? The reply is, bhakto 'si: "The only qualification is that you are My devotee. That's all."