yat tu kṛtsna-vad ekasmin
kārye saktam ahaitukam
atattvārtha-vad alpaḿ ca
tat tāmasam udāhṛtam

Translation of Bhagavad Gita 18.22

And that knowledge by which one is attached to one kind of work as the all in all, without knowledge of the truth, and which is very meager, is said to be in the mode of darkness.

Commentary by Sri A.C. Bhaktivedanta Swami Prabhupada of Gaudiya Sampradaya:

The “knowledge” of the common man is always in the mode of darkness or ignorance because every living entity in conditional life is born into the mode of ignorance. One who does not develop knowledge through the authorities or scriptural injunctions has knowledge that is limited to the body. He is not concerned about acting in terms of the directions of scripture. For him God is money, and knowledge means the satisfaction of bodily demands. Such knowledge has no connection with the Absolute Truth. It is more or less like the knowledge of the ordinary animals: the knowledge of eating, sleeping, defending and mating. Such knowledge is described here as the product of the mode of darkness. In other words, knowledge concerning the spirit soul beyond this body is called knowledge in the mode of goodness, knowledge producing many theories and doctrines by dint of mundane logic and mental speculation is the product of the mode of passion, and knowledge concerned only with keeping the body comfortable is said to be in the mode of ignorance.

Commentary by Sri Vishvanatha Chakravarthi Thakur of Gaudiya Sampradaya:

This verse speaks of tamasic knowledge. Knowledge which is speculative only (ahaitukam) (not with reference to any scripture) which is extremely attached to performing one material activity such as eating or bathing, drinking or enjoying with a woman, with disregard for vedic activities like sacrifice, with no idea of real truth (atattva arthavat), knowledge which is scant like that of an animal, is known as tamasic knowledge.

Knowledge of tat which is different from the body is sattvika. Knowledge of scriptures of logic and such, which gives rise to various doctrines, is rajasic. Knowledge, which is only of bathing, eating and other material actions, is tamasic. This is a summary of the three types of knowledge.

Commentary by Sri Ramanuja of Sri Sampradaya:

18.22 But that knowledge which clings to a ‘single type of act’ as what ought to be done, viz., act in the form of the worship of ghosts or evil spirits yielding very small fruits, as if it yielded all fruits; that work ‘not founded on any reason for having attachment,’ because it is not a source of all fruits; ‘untrue’ because it is based on a false view of things such as seeing differentiation in the nature of the Atman; ‘insignificant’, because the worship of ghosts and evil spirits yields poor results — for such reasons knowledge of this kind is declared to be Tamasika. After having thus classified the threefold division of knowledge relating to work according to Gunas in respect of a person who is qualified for work, Sri Krsna explains the triple division of the acts that ought to be done, according to Gunas.

Commentary by Sri Sridhara Swami of Rudra Sampradaya:

Here Lord Krishna explains that knowledge in tama guna or mode of ignorance is limited to the singular idea of bodily conception as if the physical body is the actual identity of the jiva or embodied being. Animals which are driven by instinct are possessed with this ignorance. But believing that the physical body is the be all an end all is not consciousness and is fallacious and irrational without any connection to reality. Therefore such a misconception is irrelevant and inconsequential because of possessing an extremely limited scope of existence and hence produces paltry and meagre results. Such knowledge is in tama guna.

Commentary by Sri Madhvacharya of Brahma Sampradaya:

Obstinately clinging to one’s limited viewpoint without considering the vision of others is a symptom of tama guna the mode of ignorance. Also if one supposes that after acquiring wisdom and thereafter achieving moksa or liberation from material existence that a jiva or embodied is independent when in reality even a liberated being is completely dependent and subservient to the Supreme Lord, this conception would be a great offence and cause demerits. Again assuming that nothing exists beyond the jiva or embodied being and what one perceives is illusory and unmeritorious. What need then is there to emphasise the fact that the acquisition of illogical hypothesis and untenable suppositions is a source of great degradation.

Now begins the summation.

Irrational consciousness obtained from distorted and perverse conceptions far removed from perceptions of the ultimate truth have no benefit for anyone in this life or the next and are fully situated in tama guna. There is an aphorism that knowledge must be received from a proper source in the proper order. This being the case there is no necessity in itemising degraded and depraved conceptions. The cause for such degradation of consciousness is miniscule knowledge and limited understanding which consequently develops acute unawareness. For a jiva to think of themselves as omnipotent, omniscient and omnipresent on the same level as the Supreme Lord or entertain the illusion that they are the same as the Supreme Lord is the height of folly and completely devoid of all rationality and common sense. Such erroneous conclusions which stem from irrational consciousness deprives actual knowledge of its elevated position and is always immersed in tama guna. It is seen that those who follow teachings, beliefs, doctrines and philosophies opposed to the eternal and imperishable Vedic scriptures are primarily mayavadis or impersonalists whose religions are designed in such a way that they are bereft of any actual conception of the Supreme Lord to comprehend and so they either follow a creationist conception without purpose or a concoct a supreme being without qualities and attributes.

Commentary by Sri Keshava Kashmiri of Kumara Sampradaya:

That knowledge which mechanically clings to the stagnating mentality that there is nothing better than their conception, that there is nothing more to discover, that there is no other path but theirs. Who perform the most trivial types of worship merely for their own selfish goals. Who worship impersonal conceptions of God without qualities and attributes. Who worship pagan forms symbolising God. Who worship ghosts, spirits, goblins and demons. Who irrationally dedicate their lives to such mundane delusions without any tangible objective while foolishly imagining they are accomplishing results of great import. Such jivas or embodied beings are inescably enslaved in tama guna the mode of ignorance.

Commentary by Sri Adi Shankaracharya of Advaita Sampradaya:

18.22 But tat, that knowledge; is udahrtam, said to be; tamasam, born of tamas; yat, which is; saktam, confined; ekasmin, to one; karye, from, to one body or to an external image etc., krtsnavat, as though it were all, as though it comprehended everything, thinking, ‘The Self, or God, is only this much; there is nothing beyond it,’-as the naked Jainas hold that the soul conforms to and has the size of the body, or (as others hold) that God is merely a stone or wood-, remaining confined thus to one form; ahaitukam, which is irrational, bereft of logic; a-tattvarthavat, not concerned with truth-tattvartha, truth, means some-thing just as it is; that (knowledge) which has this (truth) as its object of comprehension is tattvarthavat; that without this is ; a-tattvarthavat-; and which, on account of the very fact of its being irrational, is alpam, trivial, because it is concerned with trifles or is productive of little result. This kind of knowledge is indeed found in non-discriminating creatures in whom tamas predominates. Now is being stated the threehold division of action:

Commentary by Sri Abhinavagupta of Kaula Tantra Sampradaya:

18-20-22 Sarvabhutesu etc. upto samudahrtam. In the classified ones : i.e., [classified] as gods, human beings, etc. Considers as [really] different : i.e., with the thought ‘Here on this depends my pleasure; here in that lies my displeasure’. Without reason : To take recourse to wrath, desire etc., slavishly under the influence of one’s own addiction and also without examining the cause, in named as a thing born of the Tamas (Strand).

Sanskrit Shloka Without Transliteration Marks:

yat tu krtsna-vad ekasmin
karye saktam ahaitukam
atattvartha-vad alpam ca
tat tamasam udahrtam

Sanskrit to English Word for Word Meanings:

yat — that which; tu — but; kṛtsna-vat — as all in all; ekasmin — in one; kārye — work; saktam — attached; ahaitukam — without cause; atattva-artha-vat — without knowledge of reality; alpam — very meager; ca — and; tat — that; tāmasam — in the mode of darkness; udāhṛtam — is said to be.