There are different stages of devotional service and God realization. Strictly speaking, anyone who accepts the existence of God is situated in devotional service. To acknowledge that God is great is something, but not much. Lord Caitanya, preaching as an ācārya, a great teacher, taught that we can enter into a relationship with God and actually become God's friend, parent or lover. In the Bhagavad-gītā Kṛṣṇa showed Arjuna His universal form because Arjuna was His very dear friend. Upon seeing Kṛṣṇa as the Lord of the universes, however, Arjuna asked Kṛṣṇa to forgive the familiarity of his friendship. Lord Caitanya goes beyond this point. Through Lord Caitanya we can become friends with Kṛṣṇa, and there will be no limit to this friendship. We can become friends of Kṛṣṇa not in awe or adoration but in complete freedom. We can even relate to God as His father or mother. This is the philosophy not only of the Caitanya-caritāmṛta but of Śrīmad-Bhāgavatam as well. There are no other scriptures in the world in which God is treated as the son of a devotee. Usually God is seen as the almighty father who supplies the demands of His sons. The great devotees, however, sometimes treat God as a son in their execution of devotional service. The son demands, and the father and mother supply, and in supplying Kṛṣṇa the devotee becomes like a father or mother. Instead of taking from God, we give to God. It was in this relationship that Kṛṣṇa's mother, Yaśodā, told the Lord, “Here, eat this or You’ll die. Eat nicely.” In this way Kṛṣṇa, although the proprietor of everything, depends on the mercy of His devotee. This is a uniquely high level of friendship, in which the devotee actually believes himself to be the father or mother of Kṛṣṇa.
However, Lord Caitanya's greatest gift was His teaching that Kṛṣṇa can be treated as one's lover. In this relationship the Lord becomes so much attached to His devotee that He expresses His inability to reciprocate. Kṛṣṇa was so obliged to the gopīs, the cowherd girls of Vṛndāvana, that He felt unable to return their love. "I cannot repay your love," He told them. "I have no more assets to give." Devotional service on this highest, most excellent platform of lover and beloved, which had never been given by any previous incarnation or ācārya, was given by Caitanya Mahāprabhu. Therefore Kṛṣṇadāsa Kavirāja, quoting Śrīla Rūpa Gosvāmī, writes in the fourth verse of his book, "Lord Caitanya is Kṛṣṇa in a yellow complexion, and He is Śacīnandana, the son of mother Śacī. He is the most charitable personality because He came to deliver kṛṣṇa-prema, unalloyed love for Kṛṣṇa, to everyone. May you always keep Him in your hearts. It will be easy to understand Kṛṣṇa through Him."