namo jñāna-ghanāya ca
In the previous verses it has been described that although the Supreme Personality of Godhead has no material form, He accepts innumerable forms to favor His devotees and kill the demons. As stated in Śrīmad-Bhāgavatam, there are so many incarnations of the Supreme Personality of Godhead that they are like the waves of a river. The waves of a river flow incessantly, and no one can count how many waves there are. Similarly, no one can calculate when and how the different incarnations of the Lord appear according to the necessities of time, place and candidates. The Lord appears perpetually. As Kṛṣṇa says in Bhagavad-gītā (4.7):
yadā yadā hi dharmasya
glānir bhavati bhārata
tadātmānaṁ sṛjāmy aham
“Whenever and wherever there is a decline in religious practice, O descendant of Bharata, and a predominant rise of irreligion — at that time I descend Myself.” In the material world there is always the possibility of deviation from Kṛṣṇa consciousness, and therefore Kṛṣṇa and His devotees always act in various forms to curb such godlessness.
Even impersonalists who stress the knowledge feature of the Supreme Personality of Godhead want to merge in the effulgence of the Lord. Therefore, here the word jñāna-ghanāya indicates that for atheists who disbelieve in the form and existence of the Lord, all these various incarnations appear. Since the Lord comes to teach in so many forms, no one can say that there is no God. The word jñāna-ghanāya is especially used here to refer to those whose knowledge has become solidified by dint of their searching for the Lord through speculative philosophical understanding. Superficial knowledge is useless for understanding the Supreme Personality of Godhead, but when one’s knowledge becomes extremely intense and deep, one understands Vāsudeva (vāsudevaḥ sarvam iti sa mahātmā sudurlabhaḥ). A jñānī attains this stage after many, many births. Therefore the word jñāna-ghanāya is used here. The word śāntāya indicates that Lord Vāsudeva is situated in everyone’s heart but does not act with the living entity. Impersonalist jñānīs realize Vāsudeva when they are fully mature in knowledge (vāsudevaḥ sarvam iti sa mahātmā sudurlabhaḥ).