BG Chap 9 - Three types of jñāna yajña
Having explained the method of worship of the mahātmās or the ananya bhaktas, Kṛṣṇa next explains those who worship Him with a predominance of jñāna. Such persons worship Him thru sacrifice of knowledge (jñāna-yajña), thinking themselves as non different from the Lord, seeing Him in different material elements, and worshipping the Lord in the universal form. They worship Him as the one without a second, as diverse in many, and in the form of many devatās. Kṛṣṇa possesses subtle spiritual and material energies and remains one. By willing ‘Let there be many’, He is situated in variegated forms within the universe, from Brahmā down to the inanimate objects. Some persons worship Him to realize this conception. They worship Him who is actually one, but who is situated separately with material forms consisting of pradhāna, mahat-tattva and other elements, and who is situated as the form of the devatās such as Indra.
Jñāna-yajña is a process of knowledge by which one worships the Lord by identifying themselves with Him. Some worship the Lord thru the sacrifice of knowledge, denying difference, simply by contemplating the non difference of the worshipper and the object of worship. Such worship is called ahaṁgrahopāsanā. There are others who, thinking of the difference between worshipper and object of worship, worship the Lord thru sacrifice of knowledge in different external forms representing the Lord: the sun is brahman and so on. In this process called pratīkopāsanā, where one worships the vibhūtis of the Lord, the person thinks that the Supreme Lord Viṣṇu is non different from the sun, non different from Indra and non different from Soma. Still others worship the Lord as the soul of all, viśva rūpa, by doing many activities and worshiping many devatās. This worship of the totality of vibhūtis thinking Viṣṇu is everything is called viśva-rūpa upāsanā. If the same person simultaneously contemplates that He is the Lord, and He is also the servant of the Lord, just as the river going to the ocean is different and non different from the ocean, then there are only two types of jñāna yajña. Śrīla Prabhupāda categorizes these three worshippers as: (1) the monists, who worship themselves as God; (2) the worshippers of demigods, who consider any form to be the form of the Supreme Lord; (3) those who cannot conceive of anything beyond the manifestation of this material universe, and thus who worship the universal form of the Lord.