BG Chap 7 - The foolish contention of the impersonalists
Having explained the worshippers of demigods as less intelligent (alpa medhasa), Kṛṣṇa next explains how the impersonalists have no intelligence (abuddhaya) at all. The impersonalists think that the impersonal Brahman has manifested an illusory form as Kṛṣṇa. They think the Lord was impersonal before and had now assumed a personality. They do not know the transcendental form and activities of Kṛṣṇa, which are eternal and supreme. Although they study the scriptures they do not know the truth about the Lord. This is evident from their blasphemy of the Lord when they claim the scriptures talk about two levels of reality and their labeling of the Lord as saguna and nirguna. Externally they pose as great rasika devotees but one can easily see thru their veil of cheating.
One who is favored by a slight mercy of the lotus feet of the Lord can understand Him. But those who speculate are unable to know Him even though they continue to study the Vedas for many years. The unintelligent think that the formless Brahman beyond the material world had taken birth as Kṛṣṇa in the house of Vasudeva with an illusory form. They do not know the form, qualities, birth and pastimes of the Lord are eternal and beyond māyā. The Lord has an eternal form of pure goodness. His birth is just an appearance, for although He is born He is eternal. The monistic contention that ultimate truth is formless and that form is imposed does not hold true. It is clearly stated here that it is not imposed. From the Bhagavad-gītā we can clearly understand that the forms of the demigods and the form of the Supreme Lord are simultaneously existing and that Lord Kṛṣṇa is sac-cid-ānanda, eternal blissful knowledge.