The qualifications of the various orders of the caste system are enumerated in Bhagavad-gītā, and here we shall touch on them briefly. The brāhmaṇas are the highest social order, and they imbibe the modes of goodness and are engaged in the activities of equality, restraint, and forgiveness. The kṣatriyas are the second-highest social order, and they imbibe the qualities of creative passion and are engaged in the activities of public leadership as executive heads of different political and social bodies. The vaiśyas are the third social order. They imbibe mixed qualities, namely creative passion as well as the darkness of ignorance, and generally they are engaged as farmers and merchants. The śūdras are the lowest social order, inasmuch as they imbibe the modes of darkness, or ignorance, and generally take up the service of the other three social orders. As a class, the śūdras are servitors of the whole mundane social body. In the present age of darkness, which is known as the Kali-yuga, the age of quarrel, hypocrisy, and ignorance, virtually everyone is born a śūdra.
If we examine human affairs in the light of the caste system as created by the Personality of Godhead, surely we can visualize the four social orders functioning in every part of the world. In every part of the globe, wherever there is human habitation, there are some persons who have the qualifications of brāhmaṇas, and there are others who have the qualifications of kṣatriyas, vaiśyas, and śūdras. The various modes of nature are persistent in every corner of the universe, and since brāhmaṇas, kṣatriyas, and so forth are simply products of the modes of nature, how can one say that the four castes do not exist in a particular part of the world? This is absurd. In every country and at all times there have been, there are, and there will be the four social orders, according to the modes of nature.
Those who persist in the theory that the four social orders called the caste system exist only in India are totally mistaken. In all other countries, also, there are the same orders of life, under some name or other. And thus everywhere in the world, even those who are far below the qualifications of an ordinary śūdra, the fourth social order, are eligible for the transcendental service of the Personality of Godhead, Śrī Kṛṣṇa. The spiritual perfection which a qualified brāhmaṇa attains by the transcendental service of Śrī Kṛṣṇa can also be attained by anyone, even in a lower status than that of śūdra, by the same process of transcendental service to Śrī Kṛṣṇa. For this reason, Śrī Kṛṣṇa, the all-attractive Personality of Godhead, is the Absolute Truth in all creation, and Śrīmad Bhagavad-gītā is the supreme scripture within the universe. According to other scriptures such as the Purāṇas, even a caṇḍāla, or a person of the fifth social order (lower than a śūdra), becomes more than a person of the first order (a brāhmaṇa) by dint of his transcendental devotional service. The confidential teachings of the Bhagavad-gītā are therefore meant for nothing but attaining the highest perfection of human life—the transcendental service of Śrī Kṛṣṇa.
So, regardless of caste, creed, or color, everyone must adopt the process of karma-yoga, or work with transcendental results. And by so doing, everyone shall help to spiritualize all the activities of the world. By such activities, both the performer and the work performed become surcharged with spirituality and transcend the modes of nature. And as his activities become spiritualized, the performer automatically attains the qualifications of the highest social order, the brāhmaṇas. In fact, one who becomes fully spiritualized is transcendental to the modes of nature, and thus he is more than a brāhmaṇa. After all, although of the highest mundane order, the qualifications of a brāhmaṇa are not transcendental. How one can attain to the supreme transcendental knowledge simply by the performance of transcendental service to the Personality of Godhead is explained in the twenty-fourth verse of the fourth chapter of Bhagavad-gītā. It is explained there that through performance of work with transcendental results, everything becomes spiritualized. Ācārya Śaṅkara's philosophy of "pantheism," which has spread a perverted interpretation of the Vedānta maxim that the Supreme Spirit is omnipresent, nonetheless has a practical bearing on the above verse.