The Supreme Lord and His transcendental abode are both sanātana, as are the living entities, and the combined association of the Supreme Lord and the living entities in the sanātana abode is the perfection of human life. The Lord is very kind to the living entities because they are His sons. Lord Kṛṣṇa declares in Bhagavad-gītā, sarva-yoniṣu. .. ahaṁ bīja-pradaḥ pitā: "I am the father of all." Of course there are all types of living entities according to their various karmas, but here the Lord claims that He is the father of all of them. Therefore the Lord descends to reclaim all of these fallen, conditioned souls, to call them back to the sanātana eternal sky so that the sanātana living entities may regain their eternal sanātana positions in eternal association with the Lord. The Lord comes Himself in different incarnations, or He sends His confidential servants as sons or His associates or ācāryas to reclaim the conditioned souls.
Therefore, sanātana-dharma does not refer to any sectarian process of religion. It is the eternal function of the eternal living entities in relationship with the eternal Supreme Lord. Sanātana-dharma refers, as stated previously, to the eternal occupation of the living entity. Śrīpāda Rāmānujācārya has explained the word sanātana as "that which has neither beginning nor end," so when we speak of sanātana-dharma, we must take it for granted on the authority of Śrīpāda Rāmānujācārya that it has neither beginning nor end.