Karmīs, they think that "If I can satisfy the senses of this body, that is perfection of life." So there are three kinds of philosophers to make the solution of this unwanted material body, anartha. But actual solution is to remain in your spiritual body and meet the Supreme Personality of Godhead face to face and live with Him in eternal, blissful life of knowledge. That is Vaiṣṇava philosophy.
The Māyāvādī philosophy or the jñānīs and yogis and karmīs... Try to understand. The karmīs want to enjoy the senses of this body. Because the body is anartha, therefore sense gratification is another anartha. Because in this body you are enjoying certain type or certain grade of material enjoyment, sense gratification, and if you want more than that... Just like there are prescription, menu, of human food: vegetable, rice, wheat, sugar. This is actually the food for the human being. But if one hasn't got restriction within the area of the allotted foodstuff... Because we have to accept allotted foodstuff. Everything is food, but the human being has got an allotted foodstuff by the Supreme Lord. Eko yo bahūnāṁ vidadhāti kāmān. That Supreme Personality of Godhead is supplying everyone foodstuff. But not that the dogs' and hogs' foodstuff is the same for the human kind, no. Tena tyaktena bhuñjīthā (ISO 1). You should enjoy as it is allotted by the Supreme Lord. So if we transgress this law... Our constitutional position, anatomical fittings, is to eat fruit, vegetable, rice, wheat, milk or milk product. This is our constitutional position. But if we imitate the cats and dog, without any discrimination, if we eat, then my next body is ready, the hog's body or the dog's body. This is natural law. Kāraṇaṁ guṇa-saṅgo 'sya sad-asad-janma-yoniṣu (BG 13.22). As you associate with different types of material modes of nature, then you get the next body accordingly. Therefore on the whole, the body, either human body or demigod's body or cat's body or dog's body or tree's body or plant's body, it is unnecessary. Unnecessarily we have accepted this material body. Because our position is not this body. Na hanyate hanyamāne śarīre (BG 2.20). We are losing every time a particular type of body. But I am eternal. But people are so foolish, so rascal, they do not understand that "If I am eternal, why I have to change my body?" This is intelligence.