Devotional service is conducted under two categories, namely primary practice and spontaneous emotion. When one can rise to the platform of spontaneous emotion, he can make further progress by spiritual attachment, feeling, love, and many higher stages of devotional life for which there are no English words. We have tried to explain the science of devotional service in our book The Nectar of Devotion, based on the authority of Bhakti-rasāmṛta-sindhu by Śrīla Rūpa Gosvāmī.
Transcendental devotional service has five stages of reciprocation:
1. The self-realization stage just after liberation from material bondage is called the śānta, or neutral stage.
2. After that, when there is development of transcendental knowledge of the Lord's internal opulences, the devotee engages himself in the dāsya stage.
3. By further development of the dāsya stage, a respectful fraternity with the Lord develops, and above that a feeling of friendship on equal terms becomes manifest. Both these stages are called sākhya stage, or devotional service in friendship.
4. Above this is the stage of paternal affection toward the Lord, and this is called the vātsalya stage.
5. And above this is the stage of conjugal love, and this stage is called the highest stage of love of God, although there is no difference in quality in any of the above stages. The last stage, conjugal love of God, is called the mādhurya stage.
Thus He instructed Rūpa Gosvāmī in devotional science and deputed him to Vṛndāvana to excavate the lost sites of the transcendental pastimes of the Lord. After this, the Lord returned to Vārāṇasī and delivered the sannyāsīs and instructed the elder brother of Rūpa Gosvāmī. We have already discussed this.
The Lord left only eight ślokas of His instructions in writing, and they are known as the Śikṣāṣṭaka. All other literatures of His divine cult were extensively written by the Lord's principal followers, the six Gosvāmīs of Vṛndāvana, and their followers. The cult of Caitanya philosophy is richer than any other, and it is admitted to be the living religion of the day with the potency for spreading as viśva-dharma, or universal religion. We are glad that the matter has been taken up by some enthusiastic sages like Bhaktisiddhānta Sarasvatī Gosvāmī Mahārāja and his disciples. We shall eagerly wait for the happy days of Bhāgavata-dharma, or prema-dharma, inaugurated by the Lord Śrī Caitanya Mahāprabhu.