Śrīla Rūpa Gosvāmī begins his great book by offering his respectful obeisances unto Śrī Sanātana Gosvāmī, who is his elder brother and spiritual master, and he prays that Bhakti-rasāmṛta-sindhu may be very pleasing to him. He further prays that by residing in that ocean of nectar, Śrī Sanātana Gosvāmī may always feel transcendental pleasure in the service of Rādhā and Kṛṣṇa.
Let us offer our respectful obeisances to all the great devotees and ācāryas (holy teachers), who are compared to sharks in the great ocean of nectar and who do not care for the various rivers of liberation. Impersonalists are very fond of merging into the Supreme, like rivers that come down and merge into the ocean. The ocean can be compared to liberation, and the rivers to all the different paths of liberation. The impersonalists are dwelling in the river water, which eventually comes to mix with the ocean. They have no information, however, that within the ocean, as within the river, there are innumerable aquatic living entities. The sharks who dwell in the ocean do not care for the rivers which are gliding down into it. The devotees eternally live in the ocean of devotional service, and they do not care for the rivers. In other words, those who are pure devotees always remain in the ocean of transcendental loving service to the Lord and have no business with the other processes, which are compared to the rivers that only gradually come to the ocean.
Śrīla Rūpa Gosvāmī prays to his spiritual master, Śrīla Sanātana Gosvāmī, for the protection of Bhakti-rasāmṛta-sindhu—"The Ocean of the Pure Nectar of Devotional Service"—from the argumentative logicians who unnecessarily meddle in the science of service to the Lord. He compares their arguments and logic to volcanic eruptions in the midst of the ocean. In the midst of the ocean, volcanic eruptions can do very little harm, and similarly, those who are against devotional service to the Lord and who put forward many philosophical theses about the ultimate transcendental realization cannot disturb this great ocean of devotional service.
The author of Bhakti-rasāmṛta-sindhu, Śrīla Rūpa Gosvāmī, very humbly submits that he is just trying to spread Kṛṣṇa consciousness all over the world, although he humbly thinks himself unfit for this work. That should be the attitude of all preachers of the Kṛṣṇa consciousness movement, following in the footsteps of Śrīla Rūpa Gosvāmī. We should never think of ourselves as great preachers, but should always consider that we are simply instrumental to the previous ācāryas, and simply by following in their footsteps we may be able to do something for the benefit of suffering humanity.
Bhakti-rasāmṛta-sindhu is divided into four parts, just as the ocean is sometimes divided into four parts, and there are different sections within each of these four divisions. Originally, in Bhakti-rasāmṛta-sindhu, the ocean is divided like the watery ocean into east, south, west and north, while the subsections within these different divisions are called waves. As in the ocean there are always different waves, either on the eastern side, the southern side, the western side or the northern side, Bhakti-rasāmṛta-sindhu similarly has different waves. In the first part there are four waves, the first being a general description of devotional service. The second concerns the regulative principles for executing devotional service, and the third wave, devotional service in ecstasy. In the fourth is the ultimate goal, love of God. These will be explicitly described along with their different symptoms.
The authorized descriptions of bhakti, or devotional service, following in the footsteps of previous ācāryas, can be summarized in the following statement by Śrīla Rūpa Gosvāmī: "First-class devotional service is known by one's tendency to be fully engaged in Kṛṣṇa consciousness, serving the Lord favorably." The purport is that one may also be in Kṛṣṇa consciousness unfavorably, but that cannot be counted as pure devotional service. Pure devotional service should be free from the desire for any material benefit or for sense gratification, as these desires are cultivated through fruitive activities and philosophical speculation. Generally, people are engaged in different activities to get some material profit, while most philosophers are engaged in proposing transcendental realization through volumes of word jugglery and speculation. Pure devotional service must always be free from such fruitive activities and philosophical speculations. One has to learn Kṛṣṇa consciousness, or pure devotional service, from the authorities by spontaneous loving service.
This devotional service is a sort of cultivation. It is not simply inaction for people who like to be inactive or devote their time to silent meditation. There are many different methods for people who want this, but cultivation of Kṛṣṇa consciousness is different. The particular word used by Śrīla Rūpa Gosvāmī in this connection is anuśīlana, or cultivation by following the predecessor teachers (ācāryas). As soon as we say "cultivation," we must refer to activity. Without activity, consciousness alone cannot help us. All activities may be divided into two classes: one class may be for achieving a certain goal, and the other may be for avoiding some unfavorable circumstance. In Sanskrit, these activities are called pravṛtti and nivṛtti-positive and negative action. There are many examples of negative action. For instance, a diseased person has to be cautious and take medicine in order to avoid some unfavorable illness.
Those who are cultivating spiritual life and executing devotional service are always engaged in activity. Such activity can be performed with the body or with the mind. Thinking, feeling and willing are all activities of the mind, and when we will to do something, the activity comes to be manifest by the gross bodily senses. Thus, in our mental activities we should always try to think of Kṛṣṇa and try to plan how to please Him, following in the footsteps of the great ācāryas and the personal spiritual master. There are activities of the body, activities of the mind and activities of speech. A Kṛṣṇa conscious person engages his words in preaching the glories of the Lord. This is called kīrtana. And by his mind a Kṛṣṇa conscious person always thinks of the activities of the Lord—as He is speaking on the Battlefield of Kurukṣetra or engaging in His various pastimes in Vṛndāvana with His devotees. In this way one can always think of the activities and pastimes of the Lord. This is the mental culture of Kṛṣṇa consciousness.