In the Vedānta-sūtra it is said, athāto brahma jijñāsā: "Now inquire about. . . Sit down about. . . Sit down quietly and inquire about the necessity, or the aim of life." That is explained in the Śrīmad-Bhāgavatam: jīvasya tattva-jijñāsā nārtho yaś ceha karmabhiḥ, kāmasya nendriya-prītiḥ (SB 1.2.10). Kāmasya nendriya, kāma. Here it is called kāma. Kāma means lust. So because we have got this body, therefore we must have some kāma. That is a fact. You cannot avoid it. Lusty desire there is, and for the upkeep of the body the lusty desires may be fulfilled. But don't become lusty which is duṣpūram, which is never to be fulfilled. So kāmasya na indriya-prītiḥ. Just like lusty desires, generally it is with reference to sex life. So sex life is required for the physiological condition of the body. That is nature's way. Or by giving birth to some nice children, that sex life is required. Otherwise, why God has made the arrangement of sex? There is need, but not duṣpūram. Kāmasya na indriya-prītiḥ: "Don't use it for sense gratification." You use it to fulfill the real purpose. So these lusty desires, unless you live a very regulated life, then it will be duṣpūram, it will be never be fulfilled—always desire, always desire, always desire. So these demons, they accept the shelter of lusty desire which will never be fulfilled, will never be satiated.
But those who are devas, godly, their lusty desire is controlled, restricted. Therefore this varṇāśrama, four varṇas and four āśramas, this is education how to control this lusty desire. That is required. In the beginning of life, the children, beginning from five years old up to twenty-five years, they are trained up as brahmacārī. Why? Just to control the kāmaṁ duṣpūram. Kāmaṁ duṣpūram. Those who are not in bad association from childhood, if they practice celibacy, they are not disturbed. They are not disturbed. That is called brahmacārī life. Why? To train the child of a human being. Because this human life is meant for stopping the cycle of birth and death. That is the mission. Therefore śāstra says that pitā na sa syāj jananī na sā syāt, na mocayed yaḥ samupeta-mṛtyum (SB 5.5.18). A man should not desire to become a father and the woman should not desire to become a mother unless both of them have taken the vow that "I shall beget a child and stop his cycle of birth and death." This is the duty of the parents. Not that "I shall beget children like cats and dogs." There should be some meaning of the life. Samupeta-mṛtyum.