(The living entity receives a suitable body according to his material desires)
Prabhupāda: The function of human activity is to know oneself, what he is, and then begin his work. And if he works simply just like animal, eating, sleeping, mating and defending... These are animal activities. If you simply endeavor for eating whole day and night, and if you are satisfied whatever you like to eat, and you think that "My mission of life is finished, now my belly is full with foodstuff," that is not human civilization. But in this age people are degrading so much that at the end of the day, if he can have a full belly meal, he says, "Oh, I am now satisfied." Just like animal. Or "If I can sleep in a nice apartment, oh, I am very happy." Or "If I can mate with a beautiful opposite sex, oh, I am happy." These are animal happiness. Actual human happiness is not simply to meet the bodily demands. That is called brahma-jijñāsā. Athāto brahma jijñāsā ('Now is the time to inquire about the Absolute Truth').
Now where to inquire about this Brahman, about oneself, that is the next question. Just like if you want to learn something about medical science you have to approach some medical man or you have to take admission in some medical school or college. Or if you want to learn about engineering you have to seek after somebody who knows engineering or technology. That is the way of education. So many universities and department of knowledge teaching different department of knowledge. Similarly, if you want to learn about yourself, Brahman, then you have to seek after some teacher who can teach you about your self. This is common knowledge. This is common knowledge. So all the Vedic literature says that in order to learn that transcendental science about yourself or about God, then tad vijñānārthaṁ sa gurum evābhigacchet (MU 1.2.12). In order to learn that science, don't manufacture, but scientific way, if you want to learn... Tad vijñānārthaṁ sa gurum eva... gurum eva abhigacchet. Guru means spiritual master. Eva, eva means certainly. Not that if somebody thinks, "Oh, I can learn about myself without approaching any spiritual master." That is wrong. Actually eva, eva means certainly. One must. And this verb gacchet is used where this sense is used, "must." Gacchet, "must go," "must approach." That is the injunction of the Vedas. Similarly, the injunction of Śrīmad-Bhāgavatam is also tasmād guruṁ prapadyeta jijñāsuḥ śreya uttamam (SB 11.3.21).
Now, in order to approach a bona fide spiritual master, one must be very much disgusted with this material way of life. That is very nice qualification. Unless one is disgusted with this materialistic way of life, that actually in this materialistic way of life there is no happiness... This proposition must be convinced by one, that he should know certainly that "In the material way of life I cannot become happy." This is the first condition. Tasmād. Tasmād means "therefore." Similarly, in Vedānta-sūtra also, atha ataḥ brahma-jijñāsā. When we become fed up, disgusted with the materialistic way of life, natural inquiry is then "What is next?" That "next," in order to understand that "next," the Vedānta-sūtra says, the Vedic knowledge says that tasmād gurum evābhigacchet. Tasmād guruṁ prapadyeta. Therefore one should seek after a bona fide spiritual master and learn there. That is the Vedic injunction. So one who is actually convinced that "The materialistic way of life cannot make me happy," his duty is to seek after a bona fide spiritual master to be enlightened in the transcendental science of understanding oneself and what is God.
(Srila Prabhupada Lecture, New York, April 13, 1969)