This is Vedic culture. One may not be a brāhmaṇa . . . Brāhmaṇa is very advanced. Satya śama dama titikṣa (BG 18.42). But even kṣatriyas, they are also so advanced, so advanced we can see that he is hearing Bhagavad-gītā from Kṛṣṇa in the battlefield. How much time you can spare in the battlefield? The talk took place between the two soldiers when he was just going to throw his arrow. Śāstra sampate. Just was going to . . . he became very compassionate: "Kṛṣṇa, I have to kill my own kinsmen." And he's describing. He's describing, "What kind of sinful activities I am going to do." So just try to understand how much people were advanced. These Bhagavad-gītā talks took place between Kṛṣṇa and Arjuna in the battlefield, just on the verge of his beginning the battle. So how much time he could spare? Utmost, half an hour. Not more than that.
So within half an hour, this Bhagavad-gītā was taught to Kṛṣṇa (Arjuna), and he could understand it, and then agreed to fight: "Yes," naṣṭo mohaḥ smṛtir labdhā, kariṣye vacanaṁ tava (BG 18.73). How much advanced he was in education and learning, just imagine. At the present moment they are reading Bhagavad-gītā years after years, big, big scholars, big, big theologicians and . . . but they cannot understand. After reading Bhagavad-gītā, they are accusing Kṛṣṇa as immoral.
One professor in Oxford University, he is a student or professor of Bhagavad-gītā, has written book. Now his conclusion is that Kṛṣṇa is immoral. That means he could not understand Bhagavad-gītā. Bhagavad-gītā cannot be understood by any demon or third-class man. That is explained in the Bhagavad-gītā. Kṛṣṇa said to Arjuna that, "I am speaking to you the same Bhagavad-gītā, science of God, which I spoke millions of years ago to the sun-god, because the paramparā is lost, and I have picked up you because," bhakto 'si me priyo 'si me (BG 4.3), "you are very dear friend and bhakta."