It is not possible to imagine how far this material manifestation extends. In the material world everything is calculated by imagination or by some imperfect method, but the Vedic literatures give real information of what lies beyond the material universe. Since it is not possible to obtain information of anything beyond this material nature by experimental means, those who believe only in experimental knowledge may doubt the Vedic conclusions, for such people cannot even calculate how far this universe extends, nor can they reach far into the universe itself. That which is beyond our power of conception is called acintya, inconceivable. It is useless to argue or speculate about the inconceivable. If something is truly inconceivable, it is not subject to speculation or experimentation.
(Sri Caitanya Caritamrta-----introduction).

Revealed knowledge may in the beginning be unbelievable because of our paradoxical desire to verify everything with our tiny brains, but the speculative means of attaining knowledge is always imperfect. The perfect knowledge propounded in the revealed scriptures is confirmed by the great ācāryas, who have left ample commentations upon them; none of these ācāryas has disbelieved in the śāstras. One who disbelieves in the śāstras is an atheist, and we should not consult an atheist, however great he may be. A staunch believer in the śāstras, with all their diversities, is the right person from whom to gather real knowledge. Such knowledge may seem inconceivable in the beginning, but when put forward by the proper authority its meaning is revealed, and then one no longer has any doubts about it.
(Sri Caitanya Caritamrta------1:5:14-----purport).

If one becomes a bookworm, reading many books and scriptures and hearing many commentaries and the instructions of many men, this will produce doubt within his heart. One cannot in this way ascertain the real goal of life.
(Sri Caitanya Caritamrta------1:16:11-----translation)

One cannot understand the contradictions in Lord Caitanya's character by putting forward mundane logic and arguments. Consequently one should not maintain doubts in this connection. One should simply try to understand the inconceivable energy of Kṛṣṇa; otherwise one cannot understand how such contradictions are possible.
(Sri Caitanya Caritamrta------1:17:305-----translation).

Śrī Bhaktisiddhānta Sarasvatī Ṭhākura says that Kṛṣṇa is obtainable for the faithful, but for those who are accustomed to argue, Kṛṣṇa is far, far away. Similarly, these talks between Rāmānanda Rāya and Śrī Caitanya Mahāprabhu can be understood by a person who has firm faith. Those who are not in the disciplic succession, the asauta-panthīs, cannot have faith in these talks. They are always doubting and engaging in mental concoctions. These talks cannot be understood by such whimsical people. Transcendental topics remain far, far away from those engaged in mundane arguments. In this regard, the Vedic mantras in the Kaṭha Upaniṣad (1.2.9) state, naiṣā tarkeṇa matir āpaneyā proktānyenaiva su-jñānāya preṣṭha.
(Sri Caitanya Caritamrta------2:8:310-----purport).

Śrī Caitanya Mahāprabhu, as an ideal teacher, shows us how a disciple should deal with his spiritual master. Whenever there is doubt regarding any point, he should refer the matter to his spiritual master for clarification. Śrī Caitanya Mahāprabhu said that while chanting and dancing He had developed the kind of mad ecstasy that is possible only for a liberated soul. Yet even in His liberated position, He referred everything to His spiritual master whenever there were doubts. Thus in any condition, even when liberated, we should never think ourselves independent of the spiritual master, but must refer to him as soon as there is some doubt regarding our progressive spiritual life.
(Sri Caitanya Caritamrta------1:7:80-----purport).

At times, when doubts and restlessness assail us, we must remain fixed in our resolve. The best remedy for doubts is to seek the association of saintly persons. Saintly souls who are learned in the conclusions of the revealed scriptures and have realized the Supreme Lord can dissipate our doubts and calm our restless mind with unequivocal instructions and exemplary actions. When Kṛṣṇa conscious topics, which are both very potent and nectarean to the ears and heart, are heard and discussed in the association of saints, then faith in the Supreme Lord gradually increases, along with attraction and devotion to Him. Faith inspires initial surrender, and later, by the powerful influence of saintly association, one's faith deepens and becomes steady. Once faith becomes steady, all mental agitations and doubts clear up due to constant worship of the Lord. One then practices bhajana (chanting meditation) of a very esoteric and elevated nature, and this leads one to the stage of love of Godhead. To attain this state, saintly association is imperative; there is no substitute.
(Renunciation through Wisdom).