CC Ādi 7.39
sabe eḍāila mātra kāśīra māyāvādī
All were converted into devotees of Lord Caitanya, even the mlecchas and yavanas. Only the impersonalist followers of Śaṅkarācārya evaded Him.
In this verse it is clearly indicated that although Lord Caitanya Mahāprabhu converted Muslims and other mlecchas into devotees, the impersonalist followers of Śaṅkarācārya could not be converted. After accepting the renounced order of life, Caitanya Mahāprabhu converted many karma-niṣṭhas who were addicted to fruitive activities, many great logicians like Sārvabhauma Bhaṭṭācārya, nindakas (blasphemers) like Prakāśānanda Sarasvatī, pāṣaṇḍīs (nondevotees) like Jagāi and Mādhāi, and adhama paḍuyās (degraded students) like Mukunda and his friends. All of them gradually became devotees of the Lord, even the Pāṭhāns (Muslims), but the worst offenders, the impersonalists, were extremely difficult to convert, for they very tactfully escaped the devices of Lord Caitanya Mahāprabhu.
In describing the Kāśīra Māyāvādīs, Śrīla Bhaktisiddhānta Sarasvatī Ṭhākura has explained that persons who are bewildered by empiric knowledge or direct sensual perception, and who thus consider that even this limited material world can be gauged by their material estimations, conclude that anything that one can discern by direct sense perception is but māyā, or illusion. They maintain that although the Absolute Truth is beyond the range of sense perception, it includes no spiritual variety or enjoyment. According to the Kāśīra Māyāvādīs, the spiritual world is simply void. They do not believe in the Personality of the Absolute Truth or in His varieties of activities in the spiritual world. Although they have their own arguments, which are not very strong, they have no conception of the variegated activities of the Absolute Truth. These impersonalists, who are followers of Śaṅkarācārya, are generally known as Kāśīra Māyāvādīs (impersonalists residing in Vārāṇasī).
Near Vārāṇasī there is another group of impersonalists, who are known as Saranātha Māyāvādīs. Outside the city of Vārāṇasī is a place known as Saranātha, where there is a big Buddhist stūpa. Many followers of Buddhist philosophy live there, and they are known as Saranātha Māyāvādīs. The impersonalists of Saranātha differ from those of Vārāṇasī, for the Vārāṇasī impersonalists propagate the idea that the impersonal Brahman is truth whereas material varieties are false, but the Saranātha impersonalists do not even believe that the Absolute Truth, or Brahman, can be understood as the opposite of māyā, or illusion. According to their vision, materialism is the only manifestation of the Absolute Truth.
Factually both the Kāśīra and the Saranātha Māyāvādīs, as well as any other philosophers who have no knowledge of the spirit soul, are advocates of utter materialism. None of them have clear knowledge regarding the Absolute or the spiritual world. Philosophers like the Saranātha Māyāvādīs who do not believe in the spiritual existence of the Absolute Truth but consider material varieties to be everything do not believe that there are two kinds of nature, inferior (material) and superior (spiritual), as described in the Bhagavad-gītā. Actually, neither the Vārāṇasī nor Saranātha Māyāvādīs accept the principles of the Bhagavad-gītā, due to a poor fund of knowledge.
Since these impersonalists who do not have perfect spiritual knowledge cannot understand the principles of bhakti-yoga, they must be classified among the nondevotees who are against the Kṛṣṇa consciousness movement. We sometimes feel inconvenienced by the hindrances offered by these impersonalists, but we do not care about their so-called philosophy, for we are propagating our own philosophy as presented in Bhagavad-gītā As It Is and getting successful results. Theorizing as if devotional service were subject to their mental speculation, both kinds of Māyāvādī impersonalists conclude that the subject matter of bhakti-yoga is a creation of māyā and that Kṛṣṇa, devotional service and the devotee are also māyā. Therefore, as stated by Śrī Caitanya Mahāprabhu, māyāvādī kṛṣṇe aparādhī: “All the Māyāvādīs are offenders to Lord Kṛṣṇa.” (Cc. Madhya 17.129) It is not possible for them to understand the Kṛṣṇa consciousness movement; therefore we do not value their philosophical conclusions. However expert such quarrelsome impersonalists are in putting forward their so-called logic, we defeat them in every respect and go forward with our Kṛṣṇa consciousness movement. Their imaginative mental speculation cannot deter the progress of the Kṛṣṇa consciousness movement, which is completely spiritual and is never under the control of such Māyāvādīs.