Prahlāda Mahārāja says, "A devotee caṇḍāla is many times more elevated than an ordinary ritualistic brāhmaṇa." Indeed, such a devotee caṇḍāla can be the guru of the brāhmaṇas; this has been shown throughout history by many spiritual preceptors who were born in a low caste but who initiated persons of higher castes. So, the castes are classified according to merit and activity, but a pure devotee of the Lord is beyond all these classifications. He is transcendental to everything material. How can a person who is elevated beyond all castes, a saint, be adequately worshiped if he is worshiped only as a brāhmaṇa? Therefore one who has taken shelter of the Supreme Personality of Godhead is the recipient of all good fortune in all countries and at all times. The Bhagavad-gītā mentions this in several places.
Whatever part of this world a person belongs to, if he follows the instructions of the Supreme Lord in the Bhagavad-gītā, then he attains the transcendental platform and can become even more elevated than a brāhmaṇa. As Lord Kṛṣṇa says in the Gītā (4.24),
A person who is fully absorbed in Kṛṣṇa consciousness is sure to attain the spiritual kingdom because of his full contribution to spiritual activities, in which the consummation is absolute and that which is offered is of the same spiritual nature.
This verse explains how one can attain spiritual knowledge by performing activities that please the Supreme Lord.
Śrīpāda Śaṅkarācārya propounded the impersonal theory, citing phrases like sarvaṁ khalv idaṁ brahma: "By nature everything is Brahman, spirit." Śaṅkarācārya's theory has caused great confusion about established scriptural conclusions, but this phrase clearly supports the the Gītā verse quoted above.