The secret is that one must submissively listen to those who know perfectly the science of God, and one must begin the mode of service regulated by the preceptor. A devotee already attracted by the name, form, qualities, etc., of the Supreme Lord may be directed to his specific manner of devotional service; he need not waste time in approaching the Lord through logic. The expert spiritual master knows well how to engage his disciple's energy in the transcendental loving service of the Lord, and thus he engages a devotee in a specific devotional service according to his special tendency. A devotee must have only one initiating spiritual master because in the scriptures acceptance of more than one is always forbidden. There is no limit, however, to the number of instructing spiritual masters one may accept. Generally a spiritual master who constantly instructs a disciple in spiritual science becomes his initiating spiritual master later on.
(Sri Caitanya Caritamrta------1:1:35------purport).

The Lord is Para-brahman, or the source of the impersonal Brahma, which is His all-pervading feature of neutrality. In His personal feature, however, as the owner of all transcendental opulences, the Lord displays His partiality by taking the side of His devotees. Partiality, neutrality and all such qualities are present in God; otherwise they could not be experienced in the creation. Since He is the total existence, all things are properly adjusted in the Absolute. In the relative world such qualities are displayed in a perverted manner, and therefore we experience nonduality as a perverted reflection. Because there is no logic to explain how things happen in the realm of spirit, the Lord is sometimes described as being beyond the range of experience.
(Sri Caitanya Caritamrta------1:5:41------purport).

The fact is that the Supreme Personality of Godhead, the Supersoul, cannot be attained simply by explanations, logic and erudite scholarship. One cannot understand Him simply by one's brain substance. Even by studying all the Vedic literatures, one cannot understand the Supreme Lord. However, if one is slightly favored by the mercy of the Lord, if the Lord is pleased, one can understand Him. But who are the candidates eligible to receive the mercy of the Lord? Only the devotees. They alone can understand what is the Supreme Personality of Godhead. The Lord reveals Himself to the sincere devotee when He is pleased with his service: svayam eva sphuraty adaḥ. One should not try to understand the Lord simply from the statements of the Vedas, nor should one uselessly attempt to decry these statements through reasoning and logic.
(Sri Caitanya Caritamrta------2:6:87------purport).

All Vedic literatures declare that transcendental subjects cannot be understood simply by argument or logic. Spiritual matters are far above experimental knowledge. Only by Kṛṣṇa's mercy can one who is interested in His transcendental loving affairs understand them. If one tries to understand these transcendental topics simply by using one's material brain substance, the attempt will be futile. Whether one is a prākṛta-sahajiyā or a mundane opportunist or scholar, one's labor to understand these topics by mundane means will ultimately be frustrated. One therefore has to give up all mundane attempts and try to become a pure devotee of Lord Viṣṇu. When a devotee follows the regulative principles, the truth of these talks will be revealed to him.
(Sri Caitanya Caritamrta------2:8:310------purport).

The standard of devotion is also categorized in the same way. A neophyte believes that only love of Kṛṣṇa or Kṛṣṇa consciousness is very good, but he may not know the basis of pure Kṛṣṇa consciousness or how one can become a perfect devotee. Sometimes in the heart of a neophyte there is attraction for karma, jñāna or yoga. When he is free and transcendental to mixed devotional activity, he becomes a second-class devotee. When he becomes expert in logic and can refer to the śāstras, he becomes a first-class devotee. The devotees are also described as positive, comparative and superlative in terms of their love and attachment for Kṛṣṇa.
(Sri Caitanya Caritamrta------2:22:71------purport).

For advanced education there are various kinds of books of knowledge, such as the four Vedas, their six supplements, the Vedānta-sūtra, books of logic, books of religiosity and the Purāṇas. So all together there are fourteen divisions of books of education. Of these, the book which presents adhyātma-vidyā, spiritual knowledge—in particular, the Vedānta-sūtra—represents Kṛṣṇa.
Among logicians there are different kinds of argument. Supporting one's argument with evidence that also supports the opposing side is called jalpa. Merely trying to defeat one's opponent is called vitaṇḍā. But the actual conclusion is called vāda. This conclusive truth is a representation of Kṛṣṇa.
(Bhagavad-Gita------10:32------purport).

"The frog in the well" logic illustrates that a frog residing in the atmosphere and boundary of a well cannot imagine the length and breadth of the gigantic ocean. Such a frog, when informed of the gigantic length and breadth of the ocean, first of all does not believe that there is such an ocean, and if someone assures him that factually there is such a thing, the frog then begins to measure it by imagination by means of pumping its belly as far as possible, with the result that the tiny abdomen of the frog bursts and the poor frog dies without any experience of the actual ocean. Similarly, the material scientists also want to challenge the inconceivable potency of the Lord by measuring Him with their froglike brains and their scientific achievements, but at the end they simply die unsuccessfully, like the frog.
(Srimad Bhagavatam------2:5:10------purport).

One cannot argue, "How is it that Dhruva Mahārāja, who was prevented from getting up on the lap of his father, could press down the whole earth?" This argument is not very much appreciated by the learned, for it is an example of nagna-mātṛkā logic. By this logic one would think that because his mother in her childhood was naked, she should remain naked even when she is grown up. The stepmother of Dhruva Mahārāja might have been thinking in a similar way: since she had refused to allow him to get up on the lap of his father, how could Dhruva perform such wonderful activities as pressing down the whole earth? She must have been very surprised when she learned that Dhruva Mahārāja, by concentrating constantly on the Supreme Personality of Godhead within his heart, could press down the entire earth, like an elephant who presses down the boat on which it is loaded.
(Srimad Bhagavatam------4:8:79------purport).

A person desiring to advance in spiritual understanding should be extremely careful to avoid reading ordinary literature. The world is full of ordinary literature that creates unnecessary agitation in the mind. Such literature, including newspapers, dramas, novels and magazines, is factually not meant for advancement in spiritual knowledge. Indeed, it has been described as a place of enjoyment for crows (tad vāyasaṁ tīrtham). Anyone advancing in spiritual knowledge must reject such literature. Furthermore, one should not concern oneself with the conclusions of various logicians or philosophers. Of course, those who preach sometimes need to argue with the contentions of opponents, but as much as possible one should avoid an argumentative attitude.
(Srimad Bhagavatam------7:13:7------purport).

O demigods, fulfilling one's own interests is so important that one may even have to make a truce with one's enemies. For the sake of one's self-interest, one has to act according to the logic of the snake and the mouse.
A snake and a mouse were once caught in a basket. Now, since the mouse is food for the snake, this was a good opportunity for the snake. However, since both of them were caught in the basket, even if the snake ate the mouse, the snake would not be able to get out. Therefore, the snake thought it wise to make a truce with the mouse and ask the mouse to make a hole in the basket so that both of them could get out. The snake's intention was that after the mouse made the hole, the snake would eat the mouse and escape from the basket through the hole. This is called the logic of the snake and the mouse.
(Srimad Bhagavatam------8:6:20------translation and purport).

Śrīla Bhaktisiddhānta Sarasvatī Ṭhākura comments in this connection that people in general, in their narrow-minded conception of life, create many different types of humanitarian activities, but the humanitarian activities inaugurated by Śrī Caitanya Mahāprabhu are different. For logicians who want to accept only that which is proven through logicand argument, it is a fact that without logic and reason there can be no question of accepting the Absolute Truth. Unfortunately, when such logicians take to this path without the mercy of Śrī Caitanya Mahāprabhu, they remain on the platform of logic and argument and do not advance in spiritual life. However, if one is intelligent enough to apply his arguments and logic to the subtle understanding of the fundamental spiritual substance, he will be able to know that a poor fund of knowledge established on the basis of material logic cannot help one understand the Absolute Truth, which is beyond the reach of imperfect senses. The Mahābhārata therefore says, acintyāḥ khalu ye bhāvā na tāṁs tarkeṇa yojayet. (Mahābhārata, Bhīṣma-parva 5.22) How can that which is beyond the imagination or sensory speculation of mundane creatures be approached simply by logic? Logic and argument are very poor in spiritual strength and always imperfect when applied to spiritual understanding. By putting forward mundane logic one frequently comes to the wrong conclusion regarding the Absolute Truth, and as a result of such a conclusion one may fall down to accept a body like that of a jackal.
(Sri Caitanya Caritamrta------1:8:15------purport).

When Lord Caitanya met Sārvabhauma Bhaṭṭācārya at Jagannātha Purī, the Bhaṭṭācārya, being the greatest logician of the day, wanted to teach the Lord Vedānta philosophy. Since the Bhaṭṭācārya was an elderly man, the age of Lord Caitanya's father, He took compassion on the young sannyāsī and requested Him to learn the Vedānta-sūtra from him. Otherwise, the Bhaṭṭācārya maintained, it would be difficult for the youthful Lord Caitanya to continue as a sannyāsī. When the Lord agreed, the Bhaṭṭācārya began to teach Him in the temple of Jagannātha. The Bhaṭṭācārya spoke to the Lord about the Vedānta-sūtra continually for seven days, and the Lord heard him without speaking a word. On the eighth day the Bhaṭṭācārya said, "You have been hearing the Vedānta-sūtra from me for the past week, but You have not asked any questions, nor have You indicated whether I am explaining it nicely. So I cannot tell whether You are understanding me or not."
(Teachings of Lord Caitanya).

Thus Lord Caitanya exposed many defects in the Māyāvāda philosophy, and although the Bhaṭṭācārya tried to establish himself by logic and word jugglery, Lord Caitanya was able to defend Himself from his attacks. The Lord established that the Vedic literature is meant for three things: understanding our relationship with the Absolute Supreme Personality of Godhead, acting according to that understanding, and achieving the highest perfection of life, love of Godhead. Anyone who tries to prove that the Vedic literature aims at anything else must be a victim of his own imagination.
(Teachings of Lord Caitanya).

God's energy is beyond our conception, beyond our thinking jurisdiction, and is therefore called inconceivable (acintya). Who can argue this point? He pervades this material world and yet is beyond it. We cannot comprehend even this material world, which is insignificant compared to the spiritual world—so how can we comprehend what is beyond? Acintya means that which is beyond this material world, that which our argument, logic and philosophical speculation cannot touch, that which is inconceivable. Therefore intelligent persons, avoiding uselessargument and speculation, should accept what is stated in scriptures like the Vedas, Bhagavad-gītā and Śrīmad-Bhāgavatam and follow the principles they set down. This will lead one to understanding.
(Bhagavad-Gita-----8:9------purport).

According to learned scholars, there are three different sources of knowledge, which are called prasthāna-traya. According to these scholars, Vedānta is one of such sources, for it presents Vedic knowledge on the basis of logic and sound arguments. In the Bhagavad-gītā (13.5) the Lord says, brahma-sūtra-padaiś caiva hetumadbhir viniścitaiḥ: "Understanding of the ultimate goal of life is ascertained in the Brahma-sūtra by legitimate logic and argument concerning cause and effect." Therefore the Vedānta-sūtra is known as nyāya-prasthāna, the Upaniṣads are known as śruti-prasthāna, and the Gītā, Mahābhārata and Purāṇas are known as smṛti-prasthāna. All scientific knowledge of transcendence must be supported by śruti, smṛti and a sound logical basis.
(Sri Caitanya Caritamrta------1:7:106------purport).

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.
(Nectar of Devotion).

No one can attain the Absolute Truth by argument. One may be very expert in logic, and another person may be even more expert in the art of argument. Because there is so much word jugglery in logic, one can never come to the real conclusion about the Absolute Truth by argument. The followers of the Vedic principles understand this. However, it is seen here that Śrī Caitanya Mahāprabhu defeated the Buddhist philosophy by argument. Those who are preachers in ISKCON will certainly meet many people who believe in intellectual arguments. Most of these people do not believe in the authority of the Vedas. Nevertheless, they accept intellectual speculation and argument. Therefore the preachers of Kṛṣṇa consciousness should be prepared to defeat others by argument, just as Śrī Caitanya Mahāprabhu did. In this verse it is clearly said, tarkei khaṇḍila prabhu. Lord Śrī Caitanya Mahāprabhu put forward such a strong argument that the Buddhists could not counter Him to establish their cult.
(Sri Caitanya Caritamrta------2:9:49------purport).

An advanced devotee situated on the platform of spontaneity is already very expert in śāstric instruction, logic and argument. When he comes to the point of eternal love for Kṛṣṇa, no one can deviate him from that position, neither by argument nor by śāstric evidence. An advanced devotee has realized his eternal relationship with the Lord, and consequently he does not accept the logic and arguments of others. Such an advanced devotee has nothing to do with the sahajiyās, who manufacture their own way and commit sins by indulging in illicit sex, intoxication and gambling, if not meat-eating. Sometimes the sahajiyās imitate advanced devotees and live in their own whimsical way, avoiding the principles set down in the revealed scriptures. Unless one follows the six Gosvāmīs—Śrī Rūpa, Sanātana, Raghunātha Bhaṭṭa, Śrī Jīva, Gopāla Bhaṭṭa and Raghunātha dāsa-one cannot be a bona fide spontaneous lover of Kṛṣṇa.
(Sri Caitanya Caritamrta------2:22:153------purport).