Such foolish persons, unable to understand the spiritual activities of the Supreme Lord, consider Kṛṣṇa a product of this material nature. This is the greatest offense any human being can commit. Lord Caitanya has conclusively established that Kṛṣṇa is sac-cid-ānanda-vigraha, the form of eternity, knowledge and bliss, and that He is always engaged in His transcendental pastimes, in which there is all spiritual variegatedness.”
In this way the student of Prakāśānanda summarized the explanations of Lord Caitanya, and then he concluded: "We have given up the actual path of spiritual realization. We simply engage in nonsensical talk. Māyāvādī philosophers who are serious about attaining benediction should engage in the devotional service of Kṛṣṇa, but instead they take pleasure in useless argument only. We hereby admit that the explanation of Śaṅkarācārya hides the actual import of Vedic literature. Only the explanation given by Caitanya is acceptable. All other interpretations are useless."
(Teachings of Lord Caitanya).

Therefore Brahman realization is also not a complete understanding of the Supreme Lord. Nor is Paramātmā realization, realization of the Supersoul, full realization of the Supreme Personality of Godhead, for the all-pervading nature of the Supreme Lord is but a partial representation of His opulence.
Even the transcendental relationship experienced by a devotee of Nārāyaṇa in Vaikuṇṭha is incomplete because devotees in that relationship cannot realize the relationship between Kṛṣṇa and His devotees in Goloka Vṛndāvana. The devotees of Kṛṣṇa do not relish devotional service to Nārāyaṇa because devotional service to Kṛṣṇa is so attractive that Kṛṣṇa's devotees do not desire to worship any other form. Thus the gopīs of Vṛndāvana do not like to see Kṛṣṇa as Rukmiṇī-ramaṇa, the husband of Rukmiṇī, nor do they address Him by that name. In Vṛndāvana Kṛṣṇa is addressed as Rādhā-Kṛṣṇa—Kṛṣṇa, the property of Rādhārāṇī. Although the names Rukmiṇī-ramaṇa and Rādhā-Kṛṣṇa are on the same level in the ordinary sense, still, in the spiritual world these names indicate different understandings of various aspects of Kṛṣṇa's transcendental personality. If one equates the names Rādhā-ramaṇa or Rādhā-Kṛṣṇa with Rukmiṇī-ramaṇa, Nārāyaṇa or any other name of the Supreme Lord, he commits the fault of overlapping tastes, which is technically called rasābhāsa. Those who are expert, discriminating devotees do not accept such amalgamations, which are against the conclusions of pure devotional service. Less intelligent men think such discrimination is bigotry.
(Teachings of Lord Caitanya).

"I do not know anything," Rāmānanda Rāya replied in all humility. "I am simply saying what You are causing me to say. I know that You are Kṛṣṇa Himself, yet still You are relishing hearing about Kṛṣṇa from me. Therefore please excuse me for my faulty expression. I am just trying to express whatever You are causing me to express."
"I am a Māyāvādī sannyāsī," Lord Caitanya protested. "I have no knowledge of the transcendental features of devotional service. By the greatness of Sārvabhauma Bhaṭṭācārya My mind has become clear, and I am now trying to understand the nature of devotional service to Lord Kṛṣṇa. The Bhaṭṭācārya recommended that I see you in order to understand Kṛṣṇa. Indeed, he said that you are the only person who knows something about love of Kṛṣṇa. Therefore I have come to you upon the recommendation of Sārvabhauma Bhaṭṭācārya. Please, then, do not hesitate to relate to Me all the confidential affairs between Rādhā and Kṛṣṇa."
In this way Lord Caitanya actually took the subordinate position before Rāmānanda Rāya. This has very great significance. One who is serious about understanding the transcendental nature of Kṛṣṇa should approach a person who is actually enriched with Kṛṣṇa consciousness. One should not be proud of his material birth, material opulence, material education and material beauty and with these things try to conquer the mind of an advanced student of Kṛṣṇa consciousness.
(Teachings of Lord Caitanya).

When we speak of arguments and reason, it means arguments and reason on the basis of revealed scriptures. The first-class devotee is not interested in dry speculative methods meant for wasting time. In other words, one who has attained a mature determination in the matter of devotional service can be accepted as the first-class devotee.
The second-class devotee has been defined by the following symptoms: he is not very expert in arguing on the strength of revealed scripture, but he has firm faith in the objective. The purport of this description is that the second-class devotee has firm faith in the procedure of devotional service unto Kṛṣṇa, but he may sometimes fail to offer arguments and decisions on the strength of revealed scripture to an opposing party. But at the same time he is still undaunted within himself as to his decision that Kṛṣṇa is the supreme object of worship.
(Nectar of Devotion).

He mentions the basic principles as follows: (1) accepting the shelter of the lotus feet of a bona fide spiritual master, (2) becoming initiated by the spiritual master and learning how to discharge devotional service from him, (3) obeying the orders of the spiritual master with faith and devotion, (4) following in the footsteps of great ācāryas (teachers) under the direction of the spiritual master, (5) inquiring from the spiritual master how to advance in Kṛṣṇa consciousness, (6) being prepared to give up anything material for the satisfaction of the Supreme Personality of Godhead, Śrī Kṛṣṇa (this means that when we are engaged in the devotional service of Kṛṣṇa, we must be prepared to give up something which we may not like to give up, and also we have to accept something which we may not like to accept), (7) residing in a sacred place of pilgrimage like Dvārakā or Vṛndāvana, (8) accepting only what is necessary, or dealing with the material world only as far as necessary, (9) observing the fasting day on Ekādaśī and (10) worshiping sacred trees like the banyan tree.
(Nectar of Devotion).

As stated in Bhagavad-gītā, "A materialistic person can give up his material hankerings only by becoming situated in Kṛṣṇa consciousness." Unless one finds a superior engagement, he will not be able to give up his inferior engagement. In the material world everyone is engaged in the illusory activities of the inferior energy, but when one is given the opportunity to relish the activities of the superior energy performed by Kṛṣṇa, then he forgets all his lesser pleasures. When Kṛṣṇa speaks on the Battlefield of Kurukṣetra, to the materialistic person it appears that this is simply talk between two friends, but actually it is a river of nectar flowing down from the mouth of Śrī Kṛṣṇa. Arjuna gave aural reception to such vibrations, and thus he became freed from all the illusions of material problems.
In the Twelfth Canto of Śrīmad-Bhāgavatam, Third Chapter, verse 15, it is stated, "A person who desires unalloyed devotional service to Lord Kṛṣṇa, who is praised by transcendental sound vibrations, should always hear about His glorification and transcendental qualities. This will surely kill all kinds of inauspiciousness in the heart."
(Nectar of Devotion).

When a devotee is engaged in the service of the Lord, he is said to have reached the attainment of yoga. The English equivalent of the word yoga is "linking up." So actual linking up with Kṛṣṇa, the Supreme Personality of Godhead, begins when the devotee renders service unto Him. Devotees situated in the transcendental rasa of servitorship render their particular service whenever there is an opportunity. Sometimes they sit down in front of Kṛṣṇa to receive orders. Some persons are reluctant to accept this level of devotional service as actual bhakti-yoga, and in some of the Purāṇas also this servitorship in devotional service to Kṛṣṇa is not accepted as the actual bhakti-yoga system. But Śrīmad-Bhāgavatam has clearly indicated that the servitor relationship with Kṛṣṇa is the actual beginning of yoga realization.
(Nectar of Devotion).

Material scientists have been trying for many years, and they will go on trying for one hundred or one thousand years more, but they will never reach any planet. Maybe by a scientific process one or two men can reach some planet, but that is not the general process. The generally accepted process for transferral to other planets is the practice of the yoga system or the jñāna system. The bhakti system, however, is not meant for transferral to any material planet. Those who engage in the devotional service of Kṛṣṇa, or the Supreme Lord, are not interested in any of the planets of this material world because they know that no matter to which planet one elevates himself, he will still find the four principles of material existence there nonetheless. On some planets the duration of life is much longer than on this earth, but death is there. Those who are Kṛṣṇa conscious, however, transcend this material life of birth, death, disease and old age.
Spiritual life means release from this botheration and misery. Those who are intelligent, therefore, do not try to elevate themselves to any planet of this material world. Men are trying to reach the moon, and although it is very difficult to gain entrance to that planet, if we do gain entrance the period of our lives will be enhanced. Of course, that does not apply to life in this body. If we were to enter the moon with this body, instant death would be certain.
(Easy Journey to other Planets).