The particular business of human being is stated in the Vedānta-sūtra: athāto brahma jijñāsā. So these four principles of life, āhāra-nidrā-bhaya-maithunam, there is no difference. Only difference is a human being can inquire about what is God, or what is Brahman, athāto brahma jijñāsā. That is the only business of human life. So a cat, a dog cannot inquire about Brahman, but the gentleman inquire about what is God. Because he is human being he could inquire like that. So there is no cause of disappointment. At least our young men in India, at least still inquiring. That is the culture, "What is God?"
So this is the beginning of human life, when one inquires about Brahman. So to inquire about Brahman and to understand Brahman by proper inquiry and by proper answer from the proper source, the cultivation of this knowledge is the business of human being. Therefore a class of men in the society known as brāhmaṇa—brahma jānātīti brāhmaṇaḥ—there is need, there is necessary.