Bhagavad-gītā is the nutshell, cream of all spiritual knowledge. Here, therefore, Bhagavān, the Supreme Personality of Godhead, Kṛṣṇa, He is speaking. He is giving spiritual knowledge directly. Now, śrī-bhagavān uvāca. So there cannot be any argument. The word used here . . . Actually, this Bhagavad-gītā is described by Vyāsadeva. So Vyāsadeva recorded it, writing. Otherwise, it was being received through hearing. Before this Kali-yuga, Vyāsadeva, he kept all Vedic literature in writing. Before that, there was no book. The knowledge was received through the ear, aural reception, śruti. Therefore it is called śruti. Śruti means the knowledge which is received by hearing. And the memory was very sharp. In those days, five thousand years ago, any man . . . Not any man, but the intelligent class of men; they were called brāhmaṇas. They used to receive knowledge from guru by hearing. They could memorize everything, once heard. In the Kali-yuga the memory is being reduced. The duration of life is being reduced. Peoples' mercifulness is being reduced. This is the symptom of Kali-yuga. Bodily strength—reduced. Therefore Vyāsadeva preferred it that the Vedic knowledge should be kept recorded in writing.
So he first of all then wrote all this Vedic knowledge into writing, and the writings . . . There are the four original Vedas—Sāma, Yajur, Ṛk, Atharva—then the Upaniṣad, then the essence of Vedic knowledge, Vedānta-sūtra, then Rāmāyaṇa, Mahābhārata . . . Mahābhārata is the greater history of this planet, Bhārata. In this way immense literatures are available. If we like, we can read them. We are presenting in English translation so many books. The purpose is people of the world may know the Vedic knowledge. So essence of Vedic knowledge is this Bhagavad-gītā. Not only that; it is being spoken by the Supreme Personality of Godhead. Therefore it is said, śrī-bhagavān uvāca, so nobody could argue. Vedic knowledge means you cannot argue. You have to accept, authoritative. Just like the government literature, government regulation, when it is published, gazette, you cannot argue. Whatever the government has decided, you have to accept because government is the authority. Similarly, Vedic knowledge means you cannot argue. You can argue, but that argument is not to defeat. That argument is for understanding. Tad viddhi praṇipātena paripraśnena sevayā (BG 4.34). If you cannot understand, then you have to put questions very humbly, praṇipātena, not by challenging. Praṇipāta. Praṇipāta means very humbly submitting oneself. Praṇipātena paripraśna. Otherwise there is no need of questioning. If you have no praṇipāta . . . Praṇipāta means prakṛṣṭa-rūpeṇa nipātena, fully submissive. The answers . . . You should approach to a person, questioning, with praṇipāta, means you cannot challenge him. Whatever answer he gives, you must be prepared to accept it. Otherwise don't put question. That is the system, Vedic system. Tad viddhi praṇipātena paripraśnena (BG 4.34).