My head is the most important part of my body. Why? Because from the head all intelligence is coming. If you cut my hand, I will exist. If you cut my leg, I will exist. But if you cut my head, oh, there is no existence.
Therefore, as there is the important part of this body, the head, similarly, those who are giving intelligence to the society, they are called Brāhmins. That's all. Brāhmiṇ is not a thing which is born by, I mean to say, familywise. No. That is not . . . in the Bhagavad-gītā you'll find, cātur-varṇyaṁ mayā sṛṣṭaṁ guṇa-karma-vibhāgaśaḥ (BG 4.13).
There is no question of birthright. Anyone. Anyone. Just like in our ordinary life, anyone can become your president. It is not that a particular family has to become. One who is intelligent enough, if people like, he will be voted, he'll be elected. Similarly, according to the quality and work, the section of the society is imagined. Not imagined; practically designated.
So this Mahābhārata . . . just try to understand that Mahābhārata was originally designed for the less-intelligent class of men. Less intelligent . . . who are less-intelligent class of men? The woman class or the laborer class, and those who are born in high family but their qualities are not so improved.
Suppose a boy is born in a Brāhmin family, but his quality is just like Śūdra or laborer class. The people will not accept. Just like if I am born of a Brāhmin family, so they will ask my qualification, how I am qualified. So those who are born in high family but not qualified according to the family tradition, they are called dvija-bandhu. Dvija.
Dvija means twice-born. Dvi means two, and ja means birth. The Śudras have one birth, one birth by the father and mother.