As stated in the Eighteenth Chapter of Bhagavad-gita, sva-karmana tam abhyarcya: one has to worship the Supreme Personality of Godhead by ones occupational duties. This necessitates accepting the principle of four varnas and four asramas. Prthu Maharaja therefore says, gunaih sva-karmabhih. This phrase is explained in Bhagavad-gita. Catur-varnyam maya srstam guna-karma-vibhagasah: The four castes (the brahmanas, ksatriyas, vaisyas and sudras) are created by the Supreme Personality of Godhead according to the material modes of nature and the particular duties discharged in those modes. A person who is situated in the mode of goodness is certainly more intelligent than others. Therefore he can practice the brahminical activitiesnamely speaking the truth, controlling the senses, controlling the mind, remaining always clean, practicing tolerance, having full knowledge about ones self-identity, and understanding devotional service. In this way, if he engages himself in the loving service of the Lord as an actual brahmana, his aim to achieve the final interest of life is attained. Similarly, the ksatriyas duties are to give protection to the citizens, to give all his possessions in charity, to be strictly Vedic in the management of state affairs and to be unafraid to fight whenever there is an attack by enemies. In this way, a ksatriya can satisfy the Supreme Personality of Godhead by his occupational duties. Similarly, a vaisya can satisfy the Supreme Godhead by properly executing his occupational dutiesengaging himself in producing foodstuffs, giving protection to cows, and trading if necessary when there is an excess of agricultural production. Similarly, because sudras do not have ample intelligence, they should simply engage as workers to serve the higher statuses of social life. Everyones aim should be to satisfy the Supreme Personality of Godhead by engaging his mind in thinking always of Krsna, his words in always offering prayers to the Lord or preaching about the glories of the Lord, and his body in executing the service required to satisfy the Lord. As there are four divisions within our bodythe head, the arms, the belly and the legssimilarly, human society, taken as a whole, is divided into four classes of men according to their material qualities and occupational duties. Thus the brahminical or intelligent men have to execute the duty of the head, the ksatriyas must fulfill the duty of the arms, the vaisya class must fulfill the duty of the belly, and the sudras must fulfill the duty of the legs. In executing the prescribed duties of life, no one is higher or lower; there are such divisions as higher and lower, but since there is actually a common interestto satisfy the Supreme Personality of Godheadthere are no distinctions between them.