Brāhmaṇatva (Brahminhood, the quality or state of being a brāhmaṇa) is the goal of human evolution. Swami Ranganathananda wrote: "Evolution is human development from tamas to rajas, and from rajas to sattva. The man or woman who is all sattva is a remarkable type of person, who is highly evolved and manifesting the divine within. That is the goal of human evolution. How to produce more and more of such people in a society? Every member of society is given this goal, and he or she should try to reach it, or at least direct one’s life in that direction. Move on at your own pace, but do go towards that direction. That direction is to be a sāttvika person, without any hatred or violence, and ever loving and kind. When such persons are there in a society, there will be no need for even the police, not even for a political state, and much less need for laws and regulations, because here are persons who are self-disciplined and have realized their spiritual oneness with all others. That society is the most advanced which has the largest number of such people, who are sāttvika and spiritual and evolved, and who have manifested the divine within. Such a person is called a brāhmaṇa... The earliest definition of the word brāhmaṇa occurs in the four-thousand-year-old Bṛhadāraṇyaka Upaniṣad (3.8.10): ‘One, O Gārgī, who departs from this world without knowing this Imperishable (Reality), is miserable, a kṛpaṇaḥ. But one, O Gārgī, who departs from this world after knowing this Imperishable (Reality) is a brāhmaṇa'... In the great Buddhist book, The Dhammapada, there is a whole chapter, the last chapter, chapter 26, named Brāhmaṇa Vaggo, in praise and appreciation of the brāhmaṇa ideal" ('Universal message of the Bhagavad Gita', Vol 1, Pages 37-38).
One of the oldest Upanishads and one of the ten major Upanishads, the Chāndogya Upanishad (4.4.5), clearly demonstrates that brāhmaṇatva depends on one's qualities and not birth. Dhammapada (26.11) says: "One does not become a brāhmaṇa by one's matted hair, or by lineage, or by birth. He is a brāhmaṇa, in whom there is truth, dharma, and purity.”
Swami Vivekananda said: "Brahminhood is the ideal of humanity.., as wonderfully put forward by Shankarâchârya at the beginning of his commentary on the Gitâ, where he speaks about the reason for Krishna's coming as a preacher for the preservation of Brahminhood, of Brahminness. That was the great end. This Brahmin, the man of God, he who has known Brahman, the ideal man, the perfect man, must remain; he must not go" (Complete Works, Vol 3, Pages 293-294). Brāhmaṇatva or oneness with all beings is the fundamental yardstick of evolution.
Level of brāhmaṇatva or oneness can be used to categorize people world-over into four varṇas — brāhmaṇa, kṣatriya, vaiśya, and śūdra — in descending order of brāhmaṇatva. Varṇa is a spiritual (and not social) categorization based on one's guṇas and karma (Bhagavad-Gita, 4.13), and not based on birth. The brāhmaṇatva of a son or daughter need not be high just because the father's or mother's brāhmaṇatva is high (this can be empirically studied).
Unlike varṇa, the jāti system is a social (and not religious or spiritual) categorization, and is largely based on birth, though it may have originated as communities based on kula (clan) or gotra (lineage), or vocation. India’s jātis represent a complex, flexible and fluid system. The huge number of jātis comprise a social rather than a religious mechanism, for religious conversion does not nullify them, and they exist even for those not doing pūja of iśṭa (or worship of God). For one who is high on brāhmaṇatva or oneness, all social categorizations like jāti, kula, gotra, and vocation become irrelevant, as shown by several saints.
'Caste', as is known now, was introduced in India in the 19th century by the European colonizers. 'Caste' is a colonialist construct. The word ‘caste’ comes from the Portuguese word casta (which means lineage). 'Caste' in India was created by the British colonizers by merging varṇa, jāti, kula, gotra, and vocation, and making it illogically rigid and absolutely hereditary (for e.g., son of a weaver is a weaver even if he does not do weaving). Brahmin is a varṇa and not a jāti, but was created as a 'caste' by the colonizers. The colonizers created a hereditary and rigid 'caste' system and enforced it using the census. Most people were not aware of the 'caste' they were supposed to belong to, but were squeezed into the 'caste' system by the British colonizers in the Indian Census of 1881. The rigid hereditary 'caste' system created by the colonizers continues in India even after she regained her physical independence in 1947.
Swami Vivekananda said: "Our solution of the caste question is not degrading those who are already high up, is not running amuck through food and drink, is not jumping out of our own limits in order to have more enjoyment, but it comes... by our attaining spirituality, and by our becoming the ideal Brahmin. There is a law laid on each one of you... The command is the same to you all, that you must make progress without stopping, and that from the highest man to the lowest.., every one... has to try and become the ideal Brahmin. This... idea is applicable... over the whole world. Such is our ideal of caste as meant for raising all humanity slowly and gently towards the realisation of that great ideal of the spiritual man who is non-resisting, calm, steady, worshipful, pure, and meditative. In that ideal there is God" (Complete Works, Vol 3, Page 198).